The first thing that I notice is that by changing to a new domain name you have changed the url for all of your images. I've never studied the effect of a 301 redirect on image search, but my guess is that image search is not nearly as fast in shifting things over - even if the 301 redirects objeect for object to the new domain.
In terms of whether enhanced image search can benifit you, according to Google at the time of launch, it's "supposed to". We've had very little feedback here from site owners on the issue. Some members here have applied it on all their sites and are happy with the results, and some others won't get near it.
You can find some related threads here through Site Search [webmasterworld.com], but I can't really see anything definitive, and I don't have that kind of data of my own.