I downloaded it on the 28th and have been playing through by myself so far.
RE: Bugs, the first time a bug actually affected me was against Death, I'd be spamming my health mines and sometimes he would completely vanish after he tried to do some magic. It also affected me by being on different ground levels to when he first performed his 360 degree spell. Apart from that nothing to report! Awesome game, loads of fun, just wish I had found all my spells...
I'm playing in China at the moment, sadly no-one with any where near decent ping is near me, so single player FTW.