So, I got my unlock code from UnlockItNow.com. It arrived a little under 12 hours after purchase ($20). The email went into my junk mail box so I did not notice it until I went looking for it this morning.
The unlock worked, and now I am a happy T-Mobile customer. Now I just need to get used to the Windows Phone interface, and my years with Symbian are now just fond memories.
Just before 11:30 am today I did a few runs on speedtest.net:
Ping: 99ms -- Download: 12.37 Mbps – Upload: 13.28 Mbps
Ping: 84ms -- Download: 10.80 Mbps – Upload: 11.20 Mbps
Ping: 100ms -- Download: 12.12 Mbps – Upload: 12.17 Mbps
(Edit: forgot to mention that I am in Oakland, CA, and speedtest was running against a Berkeley, CA server.)