Well, it can't be any worse than the Sprint-Nextel merger.It would be a tougher merger due to different cell bands and technologies, but overall I think it would be a good thing so they can finally knock on the doors of Big Red and AT&T and finally do some competing to bring the overall costs to consumers down.
Also, T-Mobile USA and MetroPCS are using two different cellular technologies. The legacy MetroPCS network is CDMA based.
It may eventually improve cellular reception coverage from the combined towers and larger spectrum allocation.
I'm not convinced this merger would help consumers save money though.