I think Ray's being too critical of the game. I haven't finished it yet, but I'm finding it a fine addition to the Thief franchise.
Framerate is lower, engine is even chunkier (that's saying a lot when looking at the Dark Engine,)
I can't say anything about this, since I have yet to come across a game that doesn't get fine performance on my system. Probably it's pretty taxing on mid-to-lower-end systems. The worst issue I have is some sort of video glitch that causes walls to light up even when they should be in shadow. If I move the view to certain angles, they'll flicker from light to dark. Annoying. But as far as the graphics go overall, they are beautiful and they really capture the Thief atmosphere.
Garrett can no longer swim, rope arrows are non-existent, the climbing gloves do not consistently work,
So what, so what, and that sucks. Swimming isn't necessary to propel the Thief story, and neither are rope arrows. I don't really miss either, but yes, Thief 2 had some cool swimming parts. As for the climbing gloves, I haven't been bothered by them yet but I also haven't gotten through the game, so it sucks that they're inconsistent.
the stupid loot twinkles now,
Good! They should have made this feature one that you can toggle, but I love the twinkling loot. No more stupid loot hunts. I always hated trying to find that last piece of loot in the first two games, and picking up worthless items and having to drop them silently (which was often difficult if you haven't blackjacked the people around you). This game fixes that problem. Also, I think it's cool that Garrett is such a bad-ass thief that he can see valuable items twinkle, even in the dark. I see it like a 6th sense thing.
the mist 'o level loads completely take you out of the game,
The cut-apart levels are bad, and the misty-hallway transitions don't work well. The levels aren't constrictingly small like that other
game, but the level transitions really do detract.
there are ridiculous amounts of loot in the game (finished with over $40K),
You're complaining as a thief that there's TOO MUCH loot? This, to me, is the main sign that you're being too critical of the game, Ray. I suppose it would help if there was more to do with the loot, but I'm enjoying cleaning out every level I come across.
the NPCs magically respawn,
In town between levels? The reason the people "respawn" is because days are passing. I think it would be far more rediculous to blackjack people in town and then the next day they're still lying there (or worse, the town is empty for the rest of the game). Perhaps you're talking about something else that I just haven't gotten to yet.
the AI occasionally just wigs out, etc.
The AI does have some problems. I think they should crank up the awareness on the AI, since they're too easy to fool and hide from. Also, if you don't want to be the sneaky type, it's too easy to go someplace that the AI can't reach and pick them off one by one while they just stand there. In general, the AI has been decent for me. The difficulty in this game really comes from self-imposed rules for thieving since the AI is way too easy to hide from, even when they're actively searching for you, though.
The game has so many good points. The sound is excellent, the atmosphere awesome, the interactive-story components are top notch, the voice acting is great, and I could go on. It's not a revolution or an evolution of the series or genre, but it's really worth buying, and a Thief fan shouldn't pass up this game. And finally the fire arrows are affected by gravity!