After a quick delete of my .kde4 folder to clear an old test, I’m writing this from within KDE 4.1 RC1.
For me, it’s gone from being a contender alongside 3.5.9 to being my preferred choice. I migrate tomorrow 
With the exception of Firefox3 (which still renders horribly), everything looks perfect. While it’s perhaps a personal choice of taste, for me, font rendering is excellent. Desktop effects work without any pain.
The final feature (being able to move icons in the taskbar after they’ve been placed) is the only thing I’m waiting for (well that and Wallpaper slideshows which I can’t find anymore ). KDE3 applications work seamlessly so there’s little else stopping me from swapping over. It does what I want it to do, and it does it well. I’ve found the improvements (and stability) over beta2 are marked.
To the naysayers, a great big raspberry. To the KDE developers, I just wanted to offer a big hug and thankyou, there’s much here to be thankful for. I’m hoping more and more see the bigger picture, folder view filters are such a great feature, I’m sure there are more I haven’t yet seen.
Thankyou for making the new KDE home again.
Kay