Image Trace might work great for vectorizing color photos, but it is terrible at vectorizing complex B&W illustrations. Live Trace in CS2-CS5 was great at this. It's crazy that a new feature would break a previous functionality.
This is a pen & ink style illustration I was going to vectorize so that it would be easier to set up for a t-shirt:
As you can see from this comparison image, Live Trace does a much better job at converting this illustration to vector. It's very close to the original and has a very clean appearance. After trying every setting possible, this is the best result I could manage in Image Trace:
It seems like Image Trace can't handle the complexity that Live Trace used to work so well with. I noticed if I cropped out just the chicken, Image Trace did a better job with just that part of it. Live Trace could handle the entire thing, though, and cropping an image in to sections just adds more steps and more work.
Whatever engine Live Trace used to have, please please please add it back in for B&W art vectorizing. Right now I have to keep my old copy of CS4 installed just so I can use Live Trace. It seems like this is a problem that people have been mentioning: http://forums.adobe.com/message/5908553