I've uncovered lots of bugs and still continue to do so....most have been reported to them and TFS items created and it really drags waiting to get a workaround for one bug, only for another to spring up elsewhere.

I'm still in the middle of an upgrade 2 months after starting it.

My advice is, do a staged migration to a different server, too many bugs to do on a live server.

It seems that we the customers are doing the testing for K2, rather than them !