Nearly perfect, with a nice Sleep Timer feature letting you set volume level and time period for iTunes to play while you go to sleep. The Alarm options to wake you back up are several, and again you can set a different volume level than the one played at bedtime by the Sleep Timer -- essential for heavy sleepers like me. I crank the wake-up volume to max and Sleep Timer volume way down -- terrifies the neighbours and the cat in the morning when the Alarm mode kicks in, but manages to wake me.

The Energy Saver issue is the only drawback, and a minor one IMHO. You have to make sure your Energy Saver panel in the Mac's System Preferences is set to put the computer to sleep "Never", cuz if it does, iAlarm can't wake the beast back up to play the alarm.

You can use iAlarm's built-in energy-saver feature to put the Mac to sleep in a way that will allow iAlarm to wake it back up on time and play the alarm, but only at the expense of not being able to use the Sleep Timer feature, which is my main use of iAlarm. The trade-off is OK with me, but prevents me from giving iAlarm a 100% excellent rating. It only gets 95% -- still pretty good and well worth the modest registration fee, or delayed startup and reminder message if you don't register.