My Virgin required me to buy $20 every month. I've gone over to Verizon which requires me to buy $15 every month--I don't really use it that much.
I found Virgin kind of annoying. Their "help" seems to be oriented to younger people--like if you call to "top up" or have a question. Their phone trees were especially annoying IMO.
I'm not a texter so it might be a good choice.