About Power infusion... I have it bind to a macro with mouse over target. And I use power aura to tell me when is up (only in raids or combat). If you want you can find the code on my blog:

http://holynovanow.wordpress.com/2009/10/31/power-auras-u-cant-not-to-love-it-1/

hugs, Bati

Bob has some macros:
http://bobturkey.wordpress.com/2009/01/10/priestly-macros/

Lemme see if I can give a few suggestions.

What you said about bubbling-a common mistake that Disc priests make. Good that you picked up on it so fast.
On the Penance bit, I use MSBT and it lets me know when Penance is ready.

Pain Suppression shouldn't cause your tank's aggro to drop that much...unless you have either a crappy tank or beastly dps. However, Pain Suppression is best used in raids. But I personally have never seen PS drop a tank's aggro on a boss, except for once when I PSed the tank before he had aggro. :X

I have a macro for Inner Focus and Divine Hymn. And a macro that targets myself, casts Power Infusion, and casts Prayer of Healing. The second macro I rarely use in raid because I use PI on the highest caster dps.

I have to admit, in higher content I'm not worrying myself with Borrowed Time and Grace. If it's not up, it will be soon, cause there's rarely a moment when I'm not casting.

Many opinions to follow, in no particular order! I had all these same concerns while learning Disc.

I agree with Nymarie that Borrowed Time is not something you need to plan around. If you're planning to Penance the tank and you have a moment of clarity to think of bubbling *someone* (anyone) first, you'll get an awesomely hasted penance, having cast both spells in roughly the same time it would have taken to cast one. But that's really more of an optimization thing, and shouldn't be done until your gear has you oversupplied on mana.

I also think that healing 5-mans is significantly harder than a raid. When learning, I found it best to laser-focus on my tank: keep Weakened Soul and Renew and PoM up, Penance followed by Flash Heals when damage comes, just Flash Heals if the damage is small. Five-mans are stressful because we're strong at mitigation, not reactive healing, yet keeping *everyone* automatically shielded isn't necessarily wise. And that hunter's pulling aggro while the other mobs beat on the tank, but you've only got ONE Penance... Try it out paired with a good raid healer and you could feel very differently about the spec.

I personally use a Power Aura (the sole aura I have set up in fact) to track my Penance. There are many ways to do it, depends on whether you want to know how much time is left, see an indication when it's ON or OFF cooldown, etc.

I've always found making use of Inner Focus to be annoying. I have it macroed to cast whenever I do Divine Hymn or Prayer of Healing; while I practically never cast those spells, thing are probably going badly when I do, so IF is my little emergency assist. I don't concern myself with keeping it on cooldown.

Yes, Pain Suppression is messy and risky. I don't pop it as a matter of course, certainly not on a less than raid-geared tank who doesn't have threat coming out their ears. Use it in a 5-man only to attempt a wipe prevention, or else ignore it entirely until you're more comfortable with the spec. It also pairs nicely with Power Infusion if you're using PI on a very eager DPSer. (Note one has a longer CD than the other.)

Some day I will wade slowly into the scary waters of Holy and find myself in your shoes. 8)

1. Over-Bubbling. If you use an agro status on your grid (for me the border lights up red) you may not ALWAYS get the person who's taking damage, but you can make an educated guess. So you get the full benefit of pre-bubbling someone (instead of waiting until he gets hurt) and many times it pays off. This is useful when you have adds running about and biting the face off squishies.

2. Pain suppression is VERY useful on the tank. The agro reduction isn't that bad, but it's something to watch for. You have to make sure that the tank has firm aggro and there aren't a bunch of targets to worry about. For example: on Mimiron when he plasma blasts the tank. HUGE damage spike. To be safe, the disc priest will use PS on the 2nd plasma blast and someone else will use their CD on the first plasma blast. By the 2nd blast, the tank has firm aggro and the threat reduction is inconsequential. Also useful toward the end of any fight when the boss "frenzies" (Maexxna, right before getting webbed). By then the tank has firm aggro as well.

3. I macro Inner Focus to PoH because if I have to PoH it's probably going to be extremely expensive (and yes, disc does have occasion to POH). Also if you have a better chance of crit on that POH you're more likely to get a nice Divine Aegis on 3/5 of your POH group. I macro power infusion to Penance to use on myself. Because I'm more important than everyone else.

4. Never worry about Grace. You'll drive yourself crazy.

5. For cooldowns I use tellmewhen which I find less intrusive than power auras (power auras to me screams YOUR ABILITY IS UP, USE IT NOW and I feel compelled to use the ability even if inappropriate). I use it for penance, D. Hymn, and PoM cooldowns. http://wow.curse.com/downloads/wow-addons/details/tellmewhen.aspx

Inner Focus loves Divine Hymn. Otherwise, PoH. I think those are the best uses by far.

I have a macro to cast PI on a choice spellcaster, whom I work out before the fight (often my GM mage). I'm still learning to get it going on CD, but I find it's much more effective in the hands of good DPS than for myself.

I think PS > lost aggro on the hunter should not be taken as a normal thing. The ToC hunter is a wily fellow who is hard to build aggro on. Also, I think his lightning arrows may have a random target. In general, I don't think the threat reduction component of PS is relevant anymore, excepting unusual circumstances.

When choosing who in the party to bubble, I tend to pick the melee, especially if there are encounter-specific reasons why the melee will take damage. The champions in ToC, for example, often do splash damage to melee (chain lightning, WW, and FoK poison).

When choosing to heal a DPSer or the tank, unless the tank is very low on health, I'll choose to shield the DPS > Penance the tank > flash heal the DPS. Also, Binding Heal can provide high single-target throughput if you really need to pump out the HPS.

While I play a HolyPriest I have speced into disc far enough to gain Inner Focus I have tied it, along with my troll racial 'berserking', to FH and GH just because I forget to use them, but I also have regular FH and GH on my bar for fights where I need to time when and where i uses these crucial cooldowns. That may be an option for you.

And as for an addon that tells you when cooldowns are up I use -Tell Me When- its a handy little addon that lets you have different buttons tailored to what you need, bars for those buttons and multi bars that you can easily turn on and off in the wow interface during game play (for instance if you switch between spec's and need some cooldowns for one and some for another) I also use -Clearcast- to alert me of buffs gained from trinkets or other abilities that give you a clearcast type buff.

I'm usually Holy in our raids, but I've come to prefer healing heroics as Disc.

My strategy has been simple:

Renew the tank, shield on the tank every time weakened soul falls off, PoM on cooldown, Pennance on cooldown and either toss Flash heals or shields around the group depending on the situation until the cooldowns come back again.

The reason I like Disc in 5 mans better is that it effectively gives everyone 9-10k more health with the shields.

YMMV

I almost exclusively use inner focus with divine hymn - there's usually one point in most boss fights where you know the group/raid will be taking a lot of aoe damage, a free often-critting DH makes light work of it.

I think I'm a lazy bubbler - because of the heal it comes with i tend to bubble anyone who's taken a teensy bit of damage as it then prevents the next load of damage. While mana isn't usually an issue I have noticed recently that doing this too much will cause problems if you want to haste bigger heals and everyone has weakened soul!! So I'm trying my hardest to train myself out of this.