It's Verizon. The speed seems ok at the moment...better than dial-up anyway, but I still haven't figured out how to tether it to my laptop yet. Once I get that worked out, I should be able to do some speed tests. Then I plan to get an external antenna and there are some tweaks you can do to up the speed as well.
I also found that some web pages aren't fully functional. I.e. the buttons in Yahoo mail don't work, so I can't delete messages. I need to figure out how to sync with my Yahoo mail and use the phone's mail program. I also need to track down a bunch of WAP pages since they should be easier to view/navigate.
Another thing about the phone...I'm amazed at the technology. The reviews that I read talked about how huge it is, but it's actually impressively small...when you consider that it's a cell phone, 1.3MP camera, PDA, with Wi-Fi, Bluetooth, EV-DO, and a slide-out QWERTY keyboard! It's pretty thick, but other than that, it's smaller than most PDAs.