Windows 7 is just a Vista upgrade, with the new excellent Office style interface on everything. It'll look like Vista, and work like it, as it is not a total re-write of the code as was XP-Vista.
It will be at least another year before the release.
Most other changes from Vista will be what the majority will not use, virtual disks, better server support, a new networking API, and other fiddly bits.
So is it still worth upgrading? For security & stability, yes.
