Stopped by the Sprint store at Clybourn & Armitage yesterday. I'm looking to upgrade my ancient Epic 4G (I like the build of the Evo LTE, but I've read all the worrying stuff about the signal).
Chatted up the sales guy--he said in the last week they got the go-ahead to begin working on the downtown sites in January. Before, they had been told April.
The LTE phones were all holding a 4G connection, though it wasn't all that fast (I tested the speed on this site, because I couldn't download a proper app on the demo phones. That may have been behind the slower speeds, I have no idea). On average, the speed was between 1-2 Mbps download.
FWIW, I tested the S3, the Evo, and the iPhone 5. All three had similar signal levels (about -80 dB), which was surprising to me (expected the Evo to lag the other two). Obviously, I couldn't test the ability of the phones to connect to the proper network when going in/out of a 3G/4G area.