One of the things I hate most about it is that it uses simplistic locking for profiles -- you <i>can't</i> have multiple firefox processes sharing a profile. It's infuriating if you have your ~ on NFS.<p>Safari on OS X handles it pretty decently -- you can have multiple processes (usually from using WebKit nightlies) sharing the same prefs/bookmarks/history. The only thing that pisses me off is that "Reopen all tabs from last closed session/window" gets clobbered.