I have used them for a couple of years, and have been pretty happy with the service. I have upgraded to a Kyocera smart phone, and found some disturbing issues:
The phone is pre-loaded with applications that I don't use, and can not unload. There are two problems with this. There is no room on the phone for apps that I would actually use. The core memory is nearly all used by the "nailed up" apps. The second, and more sneaky issue concerns that apps that are pre-loaded. The network "pushes" new You-Tube videos to me every day that I don't watch, but consumes metered data bits and memory that I would like to use for other things. I know that this is standard industry practice, but there is little flexibility to make the phone serve my needs - not theirs!
The wait time for customer service has been terrible. I was in the call-back queue for over 90 minutes the other day.
I-Wireless could use a roaming plan (even at a premium) that would allow use in Canada or areas outside of Sprint coverage.
Not smart enough for a smart phone.