Turbine built LOTR on the AC2 engine, which was really impressive in its efficiency and rendering capabilities. I was involved in 20 vs. 20 fights in that game and it still ran well. So, it's really a great engine.
However, I have yet to encounter an MMORPG that turbine has run well, and I played both AC1 & 2 very seriously. I was in the top 5 to 50 server-wide in AC2, was a prolific pker, and was a serious poster on the dev board. I developed consensus among high-level players on stuff that needed to be fixed so the game wouldn't be a disaster, but we were completely ignored, and the game ended up flopping very soon after release. Devs never seem to want to admit that their players often know better than they do when it comes to balancing and/or making the game better. EQ finally learned to listen to high-end players after years of not doing so.
I can remember the idiot in charge of running AC2 devoting resources to level 10-20 content, which he claimed had the most number of players, when there was a solid chunk of the playerbase in the 20s-40s. Post level 40 there was fuck-all to do except pk (for no reward) and level. So they were busy adding newb content while i was busy soloing the second toughest XP mob in the game, which was clearly intended to be group-mob. The PvP balance was also near-perfect, but they had to fuck with it. As soon as everyone got to the third continent they realized how little content the game had and they started losing accounts.
Turbine makes great games, but they always ruin them. :P I'm not sure i'd devote a lot of time to another turbine game.
FWIW, reviews rarely mean anything for MMORPGS. You just can't learn enough about the game in the short amount of time you play it for a review. All the important things, like balance and content don't get exposed for hundreds of hours, especially soon after a game launches.