Wow, thanks for the warning. I was just about to upgrade. I have an entire drive devoted to Boot Camp I'll probably be okay? It looks like there is one error situation detected during install:

http://support.apple.com/kb/HT4649

The anandtech review implies that boot camp assistant works and the boot camp drivers (a separate download) are now 4.0 but I can't actually find them, I assume the apple updater has them.

http://www.anandtech.com/show/4485/back-to-the-mac-os-x-107-...

I suspect it is probably because Lion adds a new Recovery Partition, and when it redoes the partition layout it doesn't take the boot camp partition into account. That's kind of a scary oversight.