I'm sure you've all been keeping up on the MoP stuff coming out. It sounds like it's gonna be a bit of overhaul from what we're used to. The talent thing is "eh" at best to me, theory crafters will min/max it into cookie cutter set ups soon enough. The things that stick out to me are the possible static mana pool and gear crunch.
It's an interesting theory about the mp, I had already grasped the fact that I need spirit, I don't think any healer this expansion didn't. I don't feel that this is gonna be a huge mechanic changer for healers though. Most roll with the spirit on their gear and don't reforge out of it (or maybe they do now depending on class and gear lvl). Unless they knock the legs off of spirit, I don't see a change on the horizon. Healers will still gem int and not reforge out of spirit. Now they're driving in the last nail.
I can see this leading to healers letting tanks float in later tiers. Their heals will be rather powerful and to negate any worry over regen they'll let tanks dip a little lower in 5 mans then they do now. This could lead to better tanks late expansion cause they'll be more aware of their hp while the healer is being lazy and just using a few big heals. All in all the ground work is already laid for this system according to Ghostcrawler. All the spells already work off of %mana, the only noticable changes will be the mana regen talents not currently based off of %mana.
The gear scrunch is exciting to me cause I'm a bit nostalgic and wouldn't mind seeing top tier dps numbers drop from 50k to 5k lol. Plus I think this might make it a little easier for people to pug raids and not feel totally inadequate because they're a teir behind. If it happens though I'm willing to bet money that people would still demand Xdps and if you do say .5k or 1k for example below that you're "unacceptable" instead of the current gaps we see today. I personally hop this takes effect, but hope people don't get stupid about it.