Are you using an extension cord? If so, they can rob some of the power on the way to the Bradley. Time of day and your power quality will affect top temp too. Check your voltage at the outlet you are using. It should be 115-120 volts. If its less than that, it will be harder for the Bradley to warm up.
As for the PID, last December I got a plug-n-play Auber programmable. Man it works nice, and no work for me putting parts together! I got the programmable because I do sausage, and programming it to bring up the temp every hour until I get 175 deg is really nice. Of course, I could walk outside every hour and do it myself w/ the regular model. If you're doing ribs/butt/brisket, etc, the non-programmable model will work great because you generally don't change the temp as it smokes/cooks.
When I got the PID, I removed the slider temp control from the circuit w/ a splice piece of wire.