I bought this just before going to the US. Despite ordering at the last minute, it arrived on time as described.
When there, you can use it for calls within the US (but not overseas) and you can get 4G internet access. I used a Samsung Galaxy II, and with that, I could also use it as a wifi hot spot for my PC - fantastic! I topped up while over there by buying a top up card from Walmart for 50 USD (which gives about 17 days use on a 3 dollar a day plan, although there are also cheaper plans available). You need to take a little bit of time to set it up, but it is well worth the effort in my opinion. An excellent buy.