They used to give out the ZTE N817 which was a hilariously underpowered and just plain terrible phone. Now they have the N818S which is a VAST improvement, and really not terrible at all. The storage is still pretty limited but much better and you can actually install more than 10-15 apps unlike the N817.
It was WELL worth the $25 to upgrade and I highly recommend it. I can actually live with this phone for a long time while I save up to buy a really nice one that is also compatible with their service.