I'm partial to Launcher Pro myself
It gives me the cool cube affect for the app drawer, the performance is much better then the stock UI on my Droid x and I can limit the number of screen panels (I only need 3 not the 7 the stock UI provides). Plus the home button gives me the expose like feature of seeing all of the screens and selecting which one I want.
When I get bored of TouchWiz I may have to give that a go. I've recently rooted my N1 and installed CyanogenMod 6 RC2 and love the thing even more now.
The key to my happiness was being able to root without unlocking the bootloader, saving my warranty.
If the hacking community embrace the Galaxy S as much as they have the G1/N1 I may have to get one. It would be nice to see someone get around the Droid X's controls too.