I can't say that there would be that much of a cost difference for attendees from the East Coast if the PASS summit was on this side of the country,...

You are right. Need more coffee.

What I have seen is I/O slowing due to backups being run resulting in "blocking" SPIDs.

This is of course on a seriously underpowered...

Another thing to consider is when to do full backups if your hardware is older or not very fast. The full backups can create deadlocks and hold up your server.