It does look polished, and having not tried the new Opera i would not argue about usability.

As a general consideration, having nice window previews sure looks cool(except if they are too small, in which case they look really messy), but i dont think this is an usability improvement. Mostly because a consice title would tell you just as much - in a tenth of the space. Coolness gets confused with usability a bit too often imho.