Got Mana? When we started heroic 5 mans a few weeks ago, I sure didn't. Had to stop and drink after every... single... pull. It was rare that Innervate was off cooldown for more than a minute or two, unless we were almost at a boss where it would be needed even more. Mana pots? Went through more than I want to remember. 80 Vendor Waters would last *maybe* 2 heroics. This was without a source of Replenishment though.
After a bunch of heroics 5s, the difference was signficant. Now what I really lusted after was more spell power, whether healing or nuking. And I got some. Not tons, but some. The major change in BC gear to new gear though was the basic stats, Stamina, Int and Spirit. And wow, the new gear has a TON of all those.
Once we started raiding 25s, we made a point to have 2 or 3 Replenishments in the raid. That made a massive difference. I still had to drink after a lot of pulls, but it was so much better. As new gear kept coming in, the mana issue got better and better. The thing about Replenishment is that the bigger your mana pool, the more mana you get from it. It gives you a percentage of your mana, so that makes sense.
Last night my Boomkin had over 20k mana for the first time. With 3 Replenishments in the raid, I dare say mana was almost not even a consideration. Burn baby burn! Longer boss fights I still had to drink a pot or use an innervate on occasion, but rarely.
So, got mana issues? Once your gear gets better, you probably won't anymore! Woot!