This thing rocks! I just hooked up this 3G (HSDPA) modem and was up and running in seconds. The modem is an Expresscard 34 size wireless modem card that runs on the Cingular network in the U.S. It suports HSDPA, which Cingular has rolled out in the major metro areas, and covers most of the area here in Silicon Valley. When it can't connect via HSDPA it will drop to UMTS, EDGE, or GPRS if necessary.
Novatel touts Mac compatibility, and it was indeed a snap to get things running on the Mac. Here's all that was necessary: buy the card, sign up for Broadband Connect on my Cingular account (you may want to get another line of service so you get a separate SIM card. Otherwise you'll have to use the card from your phone, and what good is that?), insert SIM card in the XU870, pop it in the Expresscard slot, and surf away!
OK, not quite that simple. When you insert the card, the Mac recognizes it and it self-configures. I'm assuming that's due to the recent update that added WWAN support to OS X. It hard-coded certain cards for each of the major carriers, including the XU870 on Cingular. So the Network Pref Pane for the Novatel HSDPA card automatically entered the right dial numbers and account names and such. I clicked connect, it connected, and I've now got very usable, fast connectivity. In my living room I'm showing only 1 bar, but connected at HSDPA/UMTS (I'm pretty sure HSPDA is only applicable to downloads). Speakeasy shows I'm still getting 998kbps down and 347kbps up. That's about as good as my DSL connection.
Assuming I can get this kind of speed in hotels and airports and other places on business trips and other out of the office locations, this is going to be great. Internet access in a hotel, which usually tends to be relatively slow and finicky, is around $30 for a 3 day stay. This service is $60 per month, unlimited. It'll pay for itself pretty quickly!
One thing to note is that Cingular will be selling a (different) Expresscard format card very soon, which I assume you'll be able to get a rebate on when you sign a Broadband Connect contract.