I dont know if this has been convered or not, but coming from a BB tour, I like having the auto on/off feature. I had it set so that I could have it turn off around 2am, and back on at 7am. It was perfect to keep me from drunk dialing or texting after bar close. It was also great when I forget to turn off the volume when I went to bed. It sucks getting woke up at 4am by a bunch of spam email.
I'm also coming from a BB and wish that you could do this. My solution has been to put the phone into airplane mode when I go to sleep, that way no incoming calls/texts/emails will wake me up, however I can leave the volume on loud so that my alarm does wake me up.
+1 for Timeriffic - Does not turn your phone off but does control most all of the other functions. As a former BB user, I don't have the memory issues requiring turning the phone off and back on with Android phones that I did with my BB.
I'm using Silent Time Lite to disable the ringer and vibrate modes for emails at night. Works for me to keep me from waking up to emails every few hours.
I'll throw out a +1 for Silent Time Lite. I'm especially a big fan of the fact that you can set "exceptions" so that if certain people call you (i.e. family in case of family emergency), their calls will still go through at normal ringer volume even though the phone is set to silent at night.
I'll throw in a suggestion for Tasker. It allows for just about any scheduling scenario you can think of. Not sure if it will do exactly what you are asking, but you could definitely schedule the phone to be in airplane mode or something to prevent the drunk dialing thing, and also turn off the ringer at the same time.