I tried restoring my iPhone 4S. After the restore completed I got an error message saying that I have an incompatible SIM. I called tech support, both Spring and Apple, and neither was able to help. I have to go to a Sprint store tomorrow to get this resolved. Just because this happened to me doesn't necessarily mean it will happen to you. I just wanted to put this out there just in case any of my fellow Sprint users want to restore their phones in an effort to fix some issues.