It always makes me cringe to pull power on a booted operating system with a hard drive. But I suppose the Apple TV is designed to take it.
I thought of that, too. In that regard, it makes me a little uneasy not knowing if it can be turned off.
By the way, yes, it does sync when in standby mode. It is even listed as a device in iTunes when in standby.
Also, I find it a little odd that they have that nice start up movie the first time you turn it on but if it is never truly off you will only see that movie once, or after a power failure. So, why go to the trouble of putting that movie on it (not to mention using up (admittedly only a little) more HD space) for something that will be seen rarely?