Installed it last night on 2 pc's - one of them via WU and the other with the standalone installer. I don't have any benchmark programs but it does seem more responsive, but that just may be a placebo effect. File copy speed, both locally and across the network, is vastly improved.
The most imp thing I'm interested in is the ability to use a different search provider other than WDS. I'd like to use Copernic/Yahoo but they will have to provide new versions that use the SP1 search API's.