I had installed Lion on the day of release, and was experiencing some problems - mainly start-up issues, slow app launching and and constant freezing. Plus my web-browser was having issues holding up.
However, I got that sorted after installing OnyX and repairing my permissions and clearing my cache.
The only issue I'm still encountering is connecting to my network server through the regular method as Lion no longer supports AFP, so each time I boot I have to connect to my NAS via smb using my browser, which is a bit tedious. Hopefully my server would receive a firmware update soon that is compatible with OS X Lion to avoid this problem