I've gotten over the fact that T-Mobile's definition of a 4G network is far from that of the official standards body for mobile broadband technology, the IEEE.

But it should be pointed out that T-Mobiles 21 and 42 mbps top speeds are theoretical and not really possible in the real world. When I asked the T-Mobile execs to get specific about the real speeds consumers should expect from the new 42 mbps HSPA+ service, they said that download speeds should be around 29-30 mbps and upload speeds should be around 5 mbps.

Our tests of the current "21 mbps" T-Mobile service in San Francisco found some fairly fast download speeds-in the 6-8 mbps range--in various areas of town. But the coverage was spotty. In many of the neighborhoods we tested in we found download speeds of less than 1 mbps.

T-Mobile was indeed getting some fast speeds during its press conference demos here in Vegas, but I'm not sure I could get those speeds a few blocks from the convention center.

T-Mobile also took some time to talk a little smack about Verizon's LTE network. They make the point that while Verizon's LTE speeds are impressive right now, the network has no data-hungry devices like smartphones and mobile hotspots connected to it. Once these begin connecting to the Verizon network, the connection speeds may decrease.