I'm planning on upgrading my environment to vmware 5.1 soon and was wondering if anyone here might know anything regarding snapshots taken prior to the upgrade:

1. Will I need to take a snap shot after all VMs are updated and start using my VMs from that as a new starting point?
2. If some of my VMs have a couple snapshots already taken on them and I have to revert at some point in time to an older snapshot that was taken prior to upgrading to 5.1, how does that affect the VM?