I can not comment on Sprint's customer service, but around here, reception was not that great. I was a bit young at the time so I didn't worry about the bill. However, when I looked in to them about 2 years ago, I asked when they expected to see 4G service here. The rep's answer shocked me. He said they were still waiting on 3G!
Eventually when I got my first contract, my girlfriend and I went to ATT as she didnt want to switch and she got much better reception on ATT then I did with sprint. It was very very rare that I ever got a proper bill. I literally had to call AT LEAST once a month, if not more, almost every single month. Between that and the constant dropped calls we finally paid to get out of our contract it was so bad. While I realize the Internet sales is a different department then wireless, we recently switch from a Residential DSL account to a Businesses DSL Account. I will not rant on and on, but the girl who I placed the order with was an idiot. She claimed no technician needed to come out. She claimed there would be no down time. She claimed there was no installation fees. Not one of those statements were true. My service was interrupted for many hours. A tech did have to come out. We did get charged $300 in installation fees. She had provided me her @att email address in case there were any problems. Well I emailed her multiple times over the course of 3 months trying to get my instillation fees waved. Along the way, I tried calling in and speaking with multiple reps and supervisors. All of which promised me the fees had been removed. Finally we get a final notice before disconnect because we refused to pay until they straightened it out. We go in the local store this time. We double check the bill against the self serve kiosk. It claimed +$300. So finally I spoke to a store supervisor, and she pulls it up in the system and claims that it was only $30 like it should be. She calls a customer service call center and check against there records.Again she came up with $30.
Now you may wonder the point of my story. As I said, this was Internet but my ATT Wireless Customer service experiences were often times similar. Often times I had to call months in a row to resolve one issue. As soon as that was fixed, there was another issue. Sure I always got credit in the end if I over paid, but when this happens 9-10 out of 12 months of the year, credit just is not good enough any more. The real bottom line here is that by switching to T-Mobile, soon you will an ATT customer. While the price is very appealing, ask your self if you want to be an ATT customer because you will not be a T-Mobile customer for to much longer.