It's not the speed you have to worry about with T-Mobile. 3g/4g is fast if there's coverage. It's the coverage part you have to worry about. That said, the coverage is pretty good in the major cities.
I was thinking about the whole LTE thing this morning. AT&T is probably the company you want to get LTE phone with right now rather than Verizon. LTE radio drains the battery like mad so you probably want to turn it off during regular use and only use it when you need it. With AT&T, you'll still get fast 3g with their HSPA+ network. With Verizon, you're stuck on their slow CDMA 3g.
I'm actually just about fed up with AT&T at this point. I've been a customer with them since they were Cingular (in 2005), but the state of their network in my city is just terrible.
1) Some towers don't work? - This is an odd issue that I have. I'll swap to a new tower, and my data connection absolutely refuses to work. I can have 5/5 bars and it acts like a dead connection. The other week, I went with a coworker to lunch, and I noticed my phone wasn't working. We were traveling back, and I watched as my phone started dropping bars.
It got to about 1 bar when it shot back up to 3-4. The sudden change pretty much meant that I swapped to a better tower (higher signal strength). I had a feeling that my phone was going to work again, and it did. I've had this same problem with various towers in my area. My phone will swap to the new tower but something is wrong with the connection that it makes and it never works until I force a reconnection (airplane mode).
2) Constantly dropping to Edge - I switched jobs, and at my new job, I only get about 1-3 bars. The issue is that I can be at 3 bars with my phone on my desk (i.e. I'm not touching it -- no attenuation), and it suddenly switches to Edge. Now, I don't mind slower speeds, but frankly
Edge doesn't work. I assume this is because AT&T is phasing out their 2G services, which means no data over Edge?
This gets really irritating when I'm using the phone, and I notice the app becomes unresponsive. I look at my connection, and it dropped to Edge. I have to put the phone into airplane mode just to get it to reconnect to the tower. It will
always reconnect with a 4G connection.
Honestly, when the new iPhone comes out, I'll probably just go with Verizon and pay the ETF with AT&T for my iPhone 4S. Verizon has LTE in my area anyway.