I got the "Clear" WiMax service. Here is a quick review of the service.
As the picture shows, Speedtest.net reports that I'm getting 7-mbps and 500-kbps up with 73-ms latency. This is competitive with wired speeds. I usually get high-speed service all around Atlanta. I also get service in Portland and Las Vegas, the other two cities currently supported. I'd guess that I will get service in future cities Clear will support.
However, coverage sucks. Signal at home sucks, even though it's in the middle of the coverage area, and occasionally I don't get coverage in other parts of Atlanta. More importantly, Clear doesn't work outside of metropolitan areas.
In contrast, while my AT&T 3G is much slower, it always works -- even in unpopulated areas. If the 3G service doesn't work, AT&T's service backs off to 2G "EDGE" dial-up speeds, so I can still at least send/receive e-mail.
The reason for Clear's coverage issues is that it can't have the same coverage as mobile phones. In the case of mobile phones, a carrier will buy spectrum from the government that covers an entire city, or possibly an entire state. That means they can put up towers wherever they want to maximize coverage and connectivity. Clear's WiMax is different. They are using the 2.5-GHz "education" band. This is spectrum given away to education institutions (high-schools, universities, churches) a few decades ago. It was intended for local education TV broadcasts, but virtually no school used it. Clear has leased this spectrum for their WiMax service. This means that coverage is spotty because they need to have to nearby school license their spectrum. This means coverage is likely never going to be as good as mobile phone coverage.
The Clear service is unlimited, so I can run BitTorrent on the connection (in theory, I haven't tried it yet). In contrast, AT&T has a bandwidth cap of around 5-gigabytes. I few months ago, I left last.fm running, exceeded the AT&T bandwidth cap, and got stuck with a $500 overage bill.
Both AT&T 3G and Clear cost roughly the same. I've got two USB Clear adapters for $55/month (so two people can use it simultaneously).
I haven't done any security yet. I'll get around to cracking the baseband adapter on my adapter, and writing software for the USRP. This will probably take a while before I get around to it.