I've only called them once to get my phone unlocked (gave it to my mom to use in Vietnam since I switched to the SIM after that to the N900). Somehow I feel that's pretty routine so it's not hard to screw it up. Another time I had a billing question, but that was also not hard to solve (just needed info as to why they were only billing us half then and half now and it turns out it's because it had to do with my gf being on her own plan before and switching over to the family plan).

Though my girlfriend says their customer service is usually good.

Every time I speak with a rep from T-Mobile I find it a very pleasurable experience. They are very conversational, eager to please, and if they didn't know the answer to my question they put me on hold for a brief moment while they researched my question.

lol yeah thats the only time i call the rep is when i need to get unlock code hahah btw the switching thing is called prorated (i called abt this issue as well)

Tmo got one of the best customer support out of all the major cell phone providers here in the states. A little bit of vodka and you can even flirt with them ladies on the phone... free of charge.