Determining wake up/bed time by sleep cycles?

Has anyone tried counting sleep cycles to determine what time to wake up or go to bed? If so, have you noticed a difference?

I've been told that a sleep cycle is roughly 90 minutes, and it's best to try to set your alarm to coincide with the end of a sleep cycle. They also recommended setting one alarm an hour and a half before you plan on getting up, and then a second alarm for the time you actually want to wake up (an hour and a half later). Since my goal is to wake up at 7:00 am, I set my first alarm for 5:30 am. At night, I turn my light off at 11:00 pm to give myself half an hour to fall asleep by 11:30 pm. That way I get in 5 full sleep cycles before my first alarm (and a total of 7.5 hours of sleep). I have no idea if there is a recommended number of sleep cycles. I only started this week, so Sunday, Monday, and Tuesday. Last night (Wednesday), I had a phone date with a friend and didn't do my normal bedtime routine. I didn't shut my light off until 11:30. I felt like I had been having an easier time waking up the rest of the week, but today was so much harder. I feel like I've been exhausted all day too, whereas my energy level seemed higher the rest of the week (or at least, I didn't come up from work and want to take a nap like I want to right now...).

I'm going to try to continue the 11:00 lights off bedtime routine, even on the weekends, to see if it makes a long term difference, but I've been wondering if any one has tried this or had any experiences with tracking/counting/planning sleep cycles.