Well, a bunch of stuff has happened. We're all waiting with bated breath for 3.3 (or rather some people are), I switched to transmute specialization (so so worth it), my druid went crit chicken, and my dear leveling priest has gone to the dark side.
First off, 3.3 (and the transmute thing)...
I'm hoping we get a couple more weeks, but I doubt it. I've been making a nice chunk of change off the epic gem market (140-160g per gem and the only gem that costs me more than 20 g in mats is the red one), and I'm not thrilled with that changing. On the plus side, I now have a miner at 450 (and hopefully her jcing will catch up soon), so if titanium ore goes through the roof I can get some of that market. But I have greatly been enjoying the log on, transmute (I keep the mats in bulk in my bags) go squee if I get a proc (I got 5 cardinal rubies once), mail to bank alt, log on to bank alt and put in AH, get 140-160 g. Repeat as needed, and occasionally check market for underpriced gems and scoop those up for more profit. In fact, the epic gem thing has paid for cold weather flying and dual spec for Lyllea, and I'm hoping that it'll pay for the same on both Monera (the druid) and Adowa (the pally).
As far as transmute mastery vs the flask mastery (or whatever it's called), flask mastery allowed me to justify using frost lotuses rather than selling them. Lotuses go for 40g or so, and a flask goes for about 30, so the guaranteed 2 proc made it economically viable. But I have lousy luck with getting frost lotuses, so I wasn't really making many flasks. However, every time I logged in, I transmuted a gem, so in the end, switching just made sense.
Now for crit chickens. I switched the druid from feral mostly because I have two heirloom cloth items, the chest and the shoulders, and I wanted them to be useful. Plus, the boomkin rotation was a bit easier to figure out, and I can heal better with boomkin gear than I could with feral. Sadly, I now know why they're also called oomkins, but it's not much of a hardship for me to have water on hand. Of course, I stripped the heirlooms off Monera so that Lyllea could use them, but once she hits 80, back to the boomkin they go. And, can I put in a vote for different forms or at least different color choices like the cat and bear forms now have? Please?
Last but not least, face-melting. I dual-specced Lyllea earlier this week, and then promptly got my face eaten by undead. I went back to disc since disc makes her hard as heck to kill if she doesn't go oom, and went on my merry leveling way. But I knew sooner or later I would have to learn to shadow for gearing purposes (a badly geared dps can be carried through heroics, but less so a healer), so I hit shadowpriest.com, got some glyphs, and figured out some semblance of a rotation/priority. I played with it for a while last night, and WOW! I can kill two to three mobs in the time it used to take me to kill one, I can still PW:S to my heart's content, and I can still heal me if stuff goes south. I love disc, but for leveling and running around, shadow beats it hands down. I do think being disc this long (and being disc in bgs) has helped me a lot in learning how to heal, but at this point I think I can safely switch to shadow for most stuff without losing what healing skills I have acquired.
Now, which spec would I recommend for leveling? If you want to heal end-game, going disc (aka lolsmite) will help you get a handle on the tools you have, especially if you wander into bgs from time to time and try to get the most heals. But once you go shadow, going back to slower pace of lolsmite will probably be frustrating. Thus, I'd go disc till 67 or so since by then you have almost all your healing spells and hopefully a good grasp on them, then dual-spec to shadow and go nuts. Heck, you could even go holy/shadow at that point if you're planning to go holy end game.