I've been using wireless cards on my laptops when traveling for years. I currently use a Verizon 3G card for my laptop.
I have to say, it's come a long way. Now, I use the 3G card instead of 802.11g when I'm on the road or even a dedicated line at a hotel - even if the place is offering it for free simply because the speed of 3G has gotten so good.
The Verizon performance at this point is as good if not better than the typical T1 speeds I get when traveling.