>We're wondering about upgrading to 100mbit ethernet around the office, I don't care one way or the other unless ODBC will be noticeably faster with the new network cards and connections, has anyone that has made the switch noticed a real 10x increase or is ODBC still a dog no matter how much bandwith you give it?

It depends on how much you have traffic over the network. If you download 10 000 records, you will see a lot of improvements.