It depends a lot on the service provider you choose such as Verizon, AT&T, Sprint, etc. They all have USB broadband modems and somewhat pricey data plans - I have one from Sprint that costs me about $60 USD per month for unlimited service (no voice, only data) and I generally get low-end DSL speeds (750Kbps to 1.5Mbps). With a good signal, it is nearly as fast as our home Earthlink DSL, but not as fast as my business AT&T DSL. Sprint provides software for Windows and Apple OSX, though they have instructions on their web site how to install it on Linux, which looks at it like a really fast USB modem. Once you get it set up wtih your network management tools on Linux it works quite well. I haven't tried it yet because my new laptop doesn't have Linux on it, but my brother-in-law did install it on his laptop last xmas and it worked just fine. Outside of Sacramento, California we were getting about 800-900Kbps which isn't too shabby.
Sometimes real fast is almost as good as real time.
Remember, Google is your friend!