the new driver should have bugfixes for the new r600 series so it should run a little slower but in a better way. anyway, if you want to use that driver again,take yast and uninstall 8.42.3. then download the ati_package from the 8.41 site (there should be somewhere around; try the ati's rss update feed if you cannot find them elsewhere), run it in a shell and create the package for your distro. if it's not there chose opensuse 10.1 and that should generate the .rpm which is to be installed via rmp -ivh. if doens't want to install it then try forcing the package.
and as a simple advice, if you don't need the sled for work upgrade to opensuse 10.3. i've tried it some days ago and it's the best precompiled distro that i've been using in the last years. now it's terrifically stable and fast and it's far better and newer than the sled 10.1 (that should be about 7-8 months old and for a linux distro that is a granny distro).
but as i've said: pass to that ONLY if you NOT NEED tools included in the sled 10.1. the sled includes some tools that you won't get in opensuse. you might ask novell's support if they provide the packages from sled 10.1 to opensuse 10.3, but i really don't think they'll do it.