Since I bought a new PC I've not had any of the problems with upgrading Ubuntu that I had with the previous box (with its very old Nvidia graphics card). However, the recent upgrade to Lucid has shown up an obscure fault. Although he rest of the system is brilliant given its cost (i.e. nothing), my wireless adapter is misbehaving, which it didn't do on earlier versions. On boot, it simply doesn't start up the connection, well, actually it does, but then drops it again. The adapter is a BlueNext USB wireless thingy. There is a bug already flagged in the Ubuntu reporting system for this one so I am not the only one.
The only workaround so far found is to plug in a different adapter (A 3COM one from other half's PC), and get the link working, then plug in the Bluenext, which will also start working, then unplug the 3COM, and the Bluenext keeps working. Most odd.
Ubuntu bug report here..