I disabled my hacks when I upgraded, then turned them on one by one to see what worked. There were 4 that I had to uninstall.
I left them all off until the major ones were upgraded.
At the present time, I have RC 2 running on my live forum with the following hacks enabled:
vbAdvanced CMPS
vbPicGallery
vbBux/vbPlaza
IBProArcade
EZ Archive Ads
And I'm running smooth as silk