I'm currently on T-Mobile, because until this came out, they had the best International Plan. I'll be switching to FI next time I'm in the States (May). Looking forward to saving ~30/mo.
I switched, and it was great. Miss my iPhone, but will use Android if I have to, to save $350-400/yr.
Actually, when I put it that way, maybe I'm regretting switching.
Heh. Well the service is great. The phone OS, not so much, but if you don't mind/like it, well worth it. :)
Bill is about $23 before data (20 base + taxes), so my bill has been around $25ish. Installed some various android tweaks to make most apps only have wifi access, and set apps I do use on cell use not to use background data on cell service, so I use very little data, but worth paying for more when needed.
Probably better options if you are solely in the US, but for International travelers, it's a no-brainer.