I'm down in Portland, Oregon and around here Clear Wireless is the best bet. It's cheap, flat rate, with unlimited data and plenty of speed for my use. I use the USB modem dongle with my MacBook (no drivers or software required under Lion OS), but they also have a "MiFi" style wireless router that any device can connect to.
My AT&T data service (don't have it anymore) had equally impressive speeds, but data caps. My Verizon iPhone 4S has terrible speed and a data cap.
Just my two cents.