If you noticed a battery performance drop after installing Signal, now is your chance to take another look. The app has been updated to disable backgrounding. I can confirm that the app did indeed run in the background in previous versions (although I didn’t notice any serious battery issues because of this), and a check of my running processes on the iPhone 4 now indicates that Signal fully quits when you exit the app.
While signal is a useful tool for investigating reception issues, I’d love to see an update that actually logged the information it collects. It would be great to be able to check the log after a dropped call and see if my reception dropped or I had switched to a different cell tower.