It does nothing spectacularly, offers very little in the areas of speed and reliability over Firefox and is broken for about 2/3's of the plug-ins you might want to use with many problems in the streaming video category.
It is less buggy than Firefox (especially in it's current incarnation) but really incompatible or bugged in a lot of other areas.
That's my experience of using it in Win 7 since it came out.
