I finally got the game and tried out the 3D. I know the game's 3D has gotten mixed reviews, but considering how much I think 3D adds to games, I figured I'd end up liking it. Unfortunately, I don't. The hit to resolution is just far too much for me. Text is blurry. I also notice quite a few reprojection artifacts, such as flat objects or strangely curved streets. To me at least, the stereoscopic mode just takes a beautiful 2D game and makes it look bad in 3D.
On the plus side, I found aiming to be easier in 3D, perhaps because the enemies (literally) stand out more and are easier to distinguish from the background.
I'm surprised that some people find the resolution loss acceptable. As I wondered earlier in this thread, perhaps the fact that I have a native 720p projector plays a role? Does the game render a native (no scaling) 1080p side by side image when set to 3D? Though I doubt it, one possibility is that the game puts out a 1080p side by side image, but my projector scales that down to 720p side by side before processing it as 3D (this is with my Xbox set to 1080p of course), giving me half 720p resolution per eye. Those who have a 1080p set wouldn't have this problem, and would have half 1080p per eye.