I think I posted in one of your other threads. I had no problems installing 2.1 over 2.0. I booted the new boot.img over ethernet and installed the 2.1 iso from my usb stick.
I made sure to get my 2.1 images+iso's from the primary rather than any mirrors as I remember some 2.0 installs had some odd issues but gettting the primary images fixed it vs mirrored images.
Since I wont pay for a rego I dont use it much. DP5.2 crashes me all the time tho

locks up solid.
runs nicer than 2.0 did tho.