I had a standing order for three of these at work from our Nextel rep, and finally got two in on Friday. I've been using it on and off all weekend, and it's quite nice. I have been having issues with the connection manager software and the device being redetected after my laptop goes in to standby. I don't usually shut down my laptop but use standby instead, and it seems to have problems with not detecting again if I put the computer in standby without disconnecting from the Sprint network then removing the device before standby, or if I insert the device before I power my laptop up from standby. I don't know if it's the U720 or my M1210, but I'll be playing with it more this week.
Also, it doesn't fit in the USB ports very securely. Feels pretty flimsy, so I'll probably stick to using the USB cable instead of plugging it in directly.
Speed is nice though. I'm demoing them for use with a set of tablet PCs that don't have PC card slots, so this is a great option for us. As for my M1210, I'd much rather have the internal option Dell just released that I'll probably pick up in the next few weeks.
I'm averaging about 500kbps here in Orlando using the Speakeasy test, and spiked over 1mbps a few times, which overall is pretty sweet.