At Michigan attendance mattered....especially if you had a foreign language class and those professors didnt play.
Skipping a lecture was no biggie, by the time I was a senior id say about 85% of them had notes on the web or were selling them at bookstores. Discussions, you had to be choosy about skipping. I say dont do it. Everyone is right you do become addicted. I had never skipped a class until I college my second semester, after I saw a friend do it. HOOKED! But if you are going to do it, try to do it in moderation, like 1 a month or 2x a semester.