Just from a brief poking about here, it doesn't seem any of you are discussing Sprint's 4G network build-out. I know a lot about it if you're interested.
Last year, under Dan Hesse, Sprint essentially invested in Clearwire through an offering of their own spectrum for this technology formerly under the name Xohm.
http://www.xohm.com/
They gave the spectrum and the build-out they'd already done with Xohm directly to Clearwire as an investment and also sit on Clearwire's board. Additionally, Clearwire got cash investments from Google, Intel, Comcast, Time Warner Cable and Brighthouse totally $3.2 billion.
The WiMax network under the new name "Clear" is being built-out as we speak, while AT&T's and Verizon's 4G launch plans, utilizing a different technology LTE, continues to get pushed further out. Verizon is more likely to get theirs off the planning board sooner than AT&T, yet still, only real-world access beginning in some cities not until 2010.
Sprint & Clearwire have plans for some of the largest cities in the U.S. THIS YEAR! Atlanta; Las Vegas; Chicago; Charlotte, N.C.; Dallas/Fort Worth; Honolulu; Philadelphia; and Seattle. The company already offers mobile WiMax in Baltimore and Portland, Ore.
Sprint has also announced additional cities itself.
So that's a quick overview. Check the video in the link I provided under "Something to think about" thread. The latter half of it demonstrates the 4G in Baltimore.