I've had a few bugs.
• Kernel Panics (complete system crash) when clicking the AirPort menu (haven't had this since the 10.5.1 update)
• Dragging icons from Stacks often seems to 'lag' and you end up with the icon floating a few CMs away from the mouse.
• The Finder's sidebar often seems to 'lock up', so nothing changes (disconnected external HDDs still appear etc...), but it can still be accessed.
• Spotlight menu often disappears up behind the Menu Bar, or right off the side of the screen so you can only see a tiny bit.
• iChat glitches (hang ups, complete crashes, keyboard unresponsiveness etc...)
• Keyboard stops working completely, no caps lock light, no num pad light, nothing, almost as though it's been disconnected (this is on a MacBook Pro). Only happened for the first time today, but a friend of mine has had the same problem quite a lot with a brand new MBP.
There have been other issues, but overall it's not as bad as lists of bugs make it out to be. In fact it's very very good. Much faster than Tiger (by miles), and the new features are great! I'm not really finding the bugs to be any major issue (there are workarounds for most of them).