I"ve been using a Tailgater for a couple of months now. The only real problem I've had is not getting a good signal on 129. The reflector is pretty small and a dark cloud can inhibit it's setup. It's a fully automatic setup, not much you can do manually to make it work other than making sure it has a clear view.
If you want to go to the point view screen and check for signal strength, I've had good luck looking at transponder 15 on 110 and 119 and transponder 29 on 129.