I had originally wanted to go back to 6.1.3 on my 4S but have since discovered that they have disabled that with the commercial release of 7. Was pretty ticked off about that. Like many others my battery life was in the toilet after upgrading to 7.
So I've tried this. Did a backup in iTunes. Put my phone in DFU mode and did a restore. That brought it straight to 7.0.3. After that it comes up asking if I want to setup a new phone or form the restore. So I selected the restore option and will see how things go. I'm thinking there may be an improvement since I had a 30 minute phone call and the battery dropped 1%.