My battery replacement went without issue (overcoming the adhesive holding the battery in place was a chore). When I attached the power cord it went into a repetitive reboot cycle - the apple logo would come up for a while, it would vibrate twice, go dark, and then repeat the cycle. I got it into reset mode and connected it to iTunes but the restore would error because the iPhone was not responding. I thought I might have damaged something so I opened it back up removed the new battery and inspected everything. All looked well. I put the battery back in and tried the restore with the same result. Based on everything I read here, I left the phone charging several hours. When I came back I tried the restore and this time it responded, the restore went through, and the iPhone is up and running.