Ubuntu Linux is getting pretty good these days. A few years back I might have said it would be nice to have the hardware support that Windows does, but in recent years I can't say I've had many issues in that department.

GNOME is pretty polished as a desktop, but once you step into the application arena, look and feel becomes hit and miss. GNOME has guidelines in this area but they're not as widely followed as the equivalents in the Mac and Windows worlds.