I agree with tickerhacker,
I believe that the phone should be able to be turned off, over night and the alarm to operate in the morning.
I have had a mobile phone for around 12 years, various Nokia's and some Sony Ericssons. and it all this time, and all these phones I have turned my phone off at night, and I do mean off, and the phone has in the morning turned itself on and raised the alarm, so to speak. That is until I got an Android.
It is a definite step backward if Android cannot achieve this simple task. Granted, most of the time it doesn't matter too much, you plug it in before you go to bed and set it to silent/airplane. However it would be simpler if you could just turn it off.
There are also times when it would be beneficial to be able to do so. For example, I'm staying over somewhere and don't have my charger with me. I want to preserve the battery, as we all know with reasonable use, you're not going to last 2 days, so 1, I'm sure the battery will last till morning to wake me, and 2 to get as much use out of the second day as I can. So I set the alarm and turn the phone off and it wakes me in the morning.
To suggest that this is a silly demand, and an alternative is an alarm clock is not a reasoned argument.
I grant you it may not be a deal breaker for most, but I can see for some that it's an issue, and it's certainly ridiculous to suggest that it is not an issue at all, when it is a clear step backward.