Today I experienced something that appeared to be suspiciously similar to this problem (missing window frames, which makes things surprisingly unuseable), but couldn’t google a solution. In the end, I removed my .kde directory (and .kderc file), restarted and things started to look a little better. The only negative was the need to reconfigure all my kde settings.

After one and a half days of use:

• one major – unrecoverable – crash in X (i.e. couldn’t even get to the console using CTRL+ALT+F[n])
• Playing with “Monitor & Display” setup in System Settings resulted in an un-useable X configuration — okay not actually Feisty’s fault, but I’m disappointed it still doesn’t work in this release — thank god for a backed up, working xorg.conf.
• OpenOffice, usplash, skype and a couple of other apps that temporarily escape my memory, have all crashed at one point during the day

So initial experience is indicating stability is significantly worse than Edgy. It’ll be interesting to see if it improves over the next few weeks/months…