People always complain here, you better get used to it...
But seriously now, I remember that a lot of the complaints were certainly justified when going from Panther to Tiger, since the released version was kinda buggy at first (though later updates fixed most of the problems).
I am hearing a lot problems now from people with blue screens (I thought this was a windows "feature" only? Though maybe that's what you get when including bootcamp)
I haven't got a problem at all when upgrading my mac though. Some Apps don't work, but those problems will probably be solved by future updates. The OS itself is very stable IMHO. Works like a charm!
That's is because the Bad Ape app .. there is a hack to resolve that problem somewhere in this boards!