I've been hearing a lot about 2E AD&D these days, which is weird that it's suddenly popped up again as a discussion topic just as I've joined a 2E game on RPOL.net.
The consensus of discussion seems to be:
A. 2E is a good clarification of the AD&D rules, clearing up some of the confusing bits and explaining rules well.
B. 2E takes everything that was evocative and inspiring about 1E and makes it bland.
C. The way 2E changes the way XP is dished out radically changes the game play.
D. 2E simply codifies changes that were already happening in 1E campaigns.
E. 2E is simpler than core 1E, if you stick to the core books only.
F. 2E is more convoluted than expanded 1E, if you include all the splat books and supplements.
G. 2E is too focused on making PCs heros, and playing through heroic quests.
H. 2E has the best assortment of interesting campaign settings.
I. 2E is very old school, and is sort of a proto-OSR, with a ton of optional rules and various play styles/campaign styles.
J. 2E is very new school, with its changed focus of game play and small rules tweaks to focus on character over setting.
Overall, I find these contradictions and opposed takes on the edition interesting. As I've mentioned before, back in the day (late 90s) we simply mixed 1E and 2E, taking what options we liked from either edition and leaving the rest. It was never a problem. If someone wanted to play a Half-Orc Assassin, they could use the 1E books. If another player wanted to run a Specialist Mage they could use the 2E books.
Each DM would have to make calls about the rules differences for their campaign (1E, UA or 2E level limits? Race/Class/Multiclass combinations allowed? A few other things). It was really never a problem. I think only one of our campaigns got close to the 1E level limits anyway.
Getting back into the 2E game on RPOL, and looking through the PHB and a couple of the Complete books, I'd actually consider using the system again. Or at least a weird modified version. Not that I'm going to revised TS&R again...at least not for a little while. But when that next revision eventually comes around, I may be taking a look at certain elements of 2E that I may have overlooked before.
Anyway, my opinion about whether 2E is "old school" or not, I'd say it's definitely the transition edition. Stick to the core books (and maybe a couple of the Complete Class books) and, with a few optional rules like XP for treasure, you get a very old school game. Add in all the supplements to 1E, and play it with a DragonLance style story campaign theme, you get a more new school game. And yes, that is not a typo, 1st Edition AD&D can be (and apparently was) played as a new school style game with a focus on character builds and story progression.
2E is the change-over point. So it both is and isn't "old school" at the same time.