Bedside Mode on my BlackBerry is the one of the main things I'll miss about it. I set up a custom sound profile (another thing I'll miss about my BB!) so that it didn't vibrate or ring or even light the LED for anything except a phone call. Then I set Bedside Mode up so that when my BB was plugged in it's cradle, it would switch to clock mode, and determine if if was later than the time I designated for Bedside Mode to kick in. If it was, it would turn off the backlight to the keyboard, dim the screen, and switch it to my custom Phone Only sound profile. The next morning, when I take it off of the cradle, it will revert back to its Normal Mode.
It did this automatically so I am never awakened by a text in the middle of the night when I forget to turn off the sounds and I never have to worry about missing an emergency call by turning all the sounds off or the radio off. Never too bright because the screen and keyboard can dim. And when I travel, I ALWAYS have my familiar alarm clock with me.
I know it's a small thing, but I am DYING for WP7 to get something like it. My wife's WP7 phone goes off a few nights a month when a late night text comes in but her mother had a stroke one night and she can't turn her phone off at night, just in case. I don't know if MS has allowed the appropriate APIs to be accessed or what but I would LOVE to have it if a third party dev can do it.