I'll be receiving my replacement on Tuesday, hopefully.
If it freezes, it's going back on Wednesday, but this time I will be asking to keep the freezing iMac while they send me a new one.
Believe what you want, but how can you say it's 95% a software problem? It could very much be a hardware problem, in which they will recall all 4850's and send out fixed ones. If it were software related, you'd think it'd be fixed by now.
If you receive a defected iMac, do us all a FAVOR and get it replaced, so Apple can KNOW and acknowledge the problem. They have yet to come public with it.