I've used it a few times over USB, but I haven't been able to get it to work over bluetooth. Lately I've been using WMWiFiRouter, because I picked up a MacBook for my primary personal laptop.
BTW, I have an AT&T 8525 with the official WM6 rom.
update: I had a reason to fire up my connection, so thought I would grab a speed test. Its running pretty slow today, but then again, I am on the 21st floor of an office building (which isn't the best place for a GSM signal.) Here are the speedtest.net results
I've seen download speeds of over 1000 using this same setup.