I can't agree with that. Windows 7 is an evolution of Windows Vista, and arguably is as stable, feature-packed and polished as Vista should have been from the start. You've only tried the beta and RC, remember there are always bugs, even in the RTM version, just takes a little while for them to be ironed out. For example, Windows XP needed SP2, just like Vista needed SP1, though I think 7 is probably better equipped and stable from the get-go.
I'm looking forward to receiving my pre order later this month, just wish I had the disk already now to install in advance while I have some time on my hands.