The amount of minutes you get also varies A LOT depending on the amount of the refill, a $25 gets about half as many minutes per dollar as a $100 refill and $50 refill is someplace in the middle. I found out the hard way, I bought $100 as 4x $25 cards, then checked each of the 3 accts our family uses and topped them up with a single $25 and was more than annoyed to find I only added something like 130 minutes for each $25 card when I normally get 1150 for $100. A $10 refill is the worst, only about 30 minutes IIRC.
I have also yet to collect the rebate on the last "free after rebate" phone. I bought it directly from Tmobiles web site, sent in everything, got a reject letter claiming the seller wasn't an authorized vendor, called and eventually got it approved, then another same as before reject letter.
The customer support is way below abysmal, its an endless phone jail filled with dead end options.
OTOH nothing is close to as cheap, and it does work ok (coverage not that great), just watch your step.