With several major new mobile broadband services launched -- or coming soon -- in the U.S., and all promising blazing performance, it can be hard to get a clear picture of what wireless speeds you will actually get when you plug in your new data card or switch on that minty fresh new handheld or netbook. The official word from AT&T Inc. (NYSE: T), Clearwire LLC (Nasdaq: CLWR), and Verizon Wireless is that their new networks will be faster than the maximum speeds offered today. But not landline-replacement kind of fast.

In fact, the fastest-sounding new network is also the one with the least known about it. Indeed, Verizon doesn’t want to talk numbers at all on its Long Term Evolution (LTE) network until it has done a lot more testing outside the lab. But we can look to other users' experiences, particularly in the case of AT&T’s planned High-Speed Packet Access (HSPA) upgrade, to glean some indication of how these networks will operate in the real-world...