In general I think it is an improvement over win7, though it is obviously not a finished product yet. The public beta comes out in Febuary, if you are interested I would wait until then.
I have been using the 64bit version on my netbook with 1GB of ram and it is noticeably faster than it was with win7 32bit Basic. But it refuses to run stable on my desktop rig, and the new Metro apps simply will not work on the netbook (something to do with 1GB of ram, or the Atom processor, not sure which).