The upgrade to WordPress 1.5.1 was pretty smooth, but I think that my pingbacks might be borked (no one will notice or care, but it’s like personal ego stroking). Other people seem to be having similar problems (bug report).
As far as I know, there are no obvious problems, other than ones that have been around for a long time. There might be some problems with the feeds, but I’m running them all through feedburner now, so hopefully it won’t matter. I think the site will work better in older browsers now (in a lot of them, it was wanting to download a php file).
Update: I don’t think the pings have been working since Dreamhost disallowed fopen.
Update 2: They weren’t working but might be now. The problem may lie with other people’s installations, just realized my test site was still using 1.5 (which is broken).