I just finished my test drive with T-Mobile, and I have to say that their network is much better than Sprint's in the Norman area. I really hope this will change once we get official Sprint Spark, but as it stands now I was getting better outdoor and indoor coverage with T-Mobile. I also took a trip to Arkansas, and in between cities T-Mobile was down to EDGE and GPRS, which was pretty much unusable. I couldn't even get a speed test to run. The signal strength was great, though, so once they finish their 2G to LTE conversion I think T-Mobile will be in a very powerful position.
When in buildings, I only occasionally fell back to HSPA+, but that was still faster than Sprint LTE. I got a maximum speeds of 38 Mbps down and 20 Mbps up. Average was about 25-30 Mbps down and 15 Mbps up. I am still hoping Sprint will get it's act together, but I'm having a hard time coming up with reasons to stick with them.
If you guys have any questions, I am more than happy to answer them!