Curioius to see what people have to say about my analysis here. I'm pretty confident in my statements, though I know I've probably missed SOMETHING.
With 3.02 upon us, we have access to the 51 point talents now and changes to the mana regen model and downranking. Also since Priest T6 gear has minimal crit, a lot of the talents lean heavily on crit. Bring on fighting with the mages!
At 70 only it's kind of hard to get all you want b/c you are missing 10 points for the ideal build.
Discipline Healing - I'd consider moving 2 points from Renewed Hope for a reduction in GHeal cast time. That being said Penance>GHeal, and I found myself casting Pennance/Renew/Shield/Flash or GHeal/Penance with minimal GHeals in there. Penance is Gheal power but for the price of a Flash Heal.  Aspiration is a must have for the reduction in Penance CD. Gheal coupled with Inner Focus for a big crit/Aegis is win though. Further Disc has an innate 5% haste built in bringing GHeal to ~2.8sec. Pain Suppression is just 1 point, so even situationally, why not nab it.
Guardian Spirit Deep Holy - I only put minimal points into Disc for Imp Fort since if I get Guardian Spirit, I wont be able to reach meditation. Also, with the changes to threat gen on tanks, you really don't need much threat reducing talents, tank threat is a non-issue for healers really. Surge of Light is amazing, especially if you can chain a few Imp Concentrations with surge mixed in there for more time out of the 5SR. Lightwell is another amazing spell now that it doesn't break on damage. Just gotta train the dps to be ready to use it instead of the usual "ill just have a healer get me".
COH TBC Spec - This is probably the most similar to the current COH spec's while still getting a few of the new toys. Serendipty and Surge of Light.
Notes: Surge of Light: great b/c it has a 50% proc rate on crits... when raid healign with COH, you're likely to proc at least 1 crit per COH, pretty regularly. Boom... free Flash Heal on the tank.
Holy Concentration/Imp Concentration: Nerfed to all hell for TBC gear. Extremely crit reliant now, however its the main way for Holy Priests to regen mana and get out of the 5 Sec Rule.
Pain Suppression: Can be used, with aspiration, multiple times in a fight. Though aggro may not be an issue for many DPS now, it can be used as a Poor Man's Soul Shatter for -5% threat on a target, as well as a OH SHIT Button on a tank.
Power Infusion: Lackluster compared to the old version, but for 1 Talent Point; sure. Good to pop on a DPS caster, or on yourself in clutch healing situations-- and with an Aspirated 1.4 min CD, even better.
Penance: Ticks at 0, 1, and 2 seconds. Fast as all hell.
Pretty solid, but I wouldn't bother putting in the points into IDS, too many buffs can overlap it. As for Silent Resolve, tank threat will be through the roof, you'll probably be better off taking the points and putting them into imp. Inner Fire.
Whoru, you're right. My issue with Imp IF is that until 71 its pretty much PVE useless, so I could move 2 of those threat points nito IF, and move IDS 2/2 into instant cast reduction... /facepalm I keep on kneejerk going after IDS from my old IDS days.
With regards to your Guardian Spirit healing spec, personally, I'd take 5/5 Divine Providence over 5/5 Empowered Healing. With the change in downranking no longer being viable, Gheals won't be our main heal in a raid setting.
Even with the downranking change i think Gheal will still be the heal we cast most since Flash heal is a to fast heal to spam and Penance has a 8second cooldown with it specced, and even if they nerf the hp of bosses in TBC a tank without heals for 8seconds in sunwell will be a dead tank.
I think Guardian spirit is a shit spell since there isnt always you can't predict a big hit on the tank in sunwell, maybe brutallus stomps but that's about it. and it has been killed without guardian spirit so i wont specc that.
My specc will probably be: http://wotlk.wowhead.com/?talent=bVhbzhZMxxcf0qihmIo if im going for CoH since with 1 pot and no meditation it will be pretty hard not going oom, especially since our shadowpriests are slacking alot..
not sure about the spirit specc yet
You also have to cast more smart heals i guess.. not wasting some spamheals like you could do with downranking