I was pleasantly surprised to find that plugging my Sprint mobile broadband dongle (it says Sierra Wireless USB 598 on the back) into my laptop running Ubuntu 9.10 worked out of the box! After plugging in, go to the network icon in the toolbar and there appeared an entry for 'Mobile Broadband'. I checked the checkbox underneath it, which took me through an easy setup wizard (selected 'USA' and 'Sprint') and it worked! Warms my heart when Ubuntu works so well.