I may not be the most objective source, since I've been using *NIX as my primary os for a long time, but I haven't had alot of problems with 3.5.1 yet. I did steer clear of opie-packagemanager. I did the following, found on this board I believe...
ipkg remove opie-packagemanager
ipkg install opie-aqpkg
Networking worked great after install, and hostap finally has monitoring extensions. YAY! It didn't lock up after multiple cf insert/removes like 3.2 had done to me. It looks nice, I like the theme. That won't last, of course, but it is a first. All in all, for a first flash of an OZ release, this has gone rather smooth.