I flew from Chicago to Wacken in 2000 and 2001. The first year I used Bock Tours, which was great. They picked me up in Hamburg, took the bus (filled with beer and a lot of cool people) to Itzehoe, and dropped me off at the hotel door. Itzehoe is about 20 minutes from the village of Wacken and there is a pickup spot in Itzehoe where a shuttle bus will take you to the festival. It was nice to have a bed to come back to after headbanging for 15+ hours a day!
In 2001 I camped with a few German friends of mine, which was an interesting experinece to say the least! It was an absolute blast (we camped again this past summer at the Bang Your Head! festival in Balingen). The pros are that you are right there and the atmosphere is fantastic (hard to describe if you haven't gone). The cons are that a tent doesn't take the place of a warm bed, and you are at the mercy of the weather. Thankfully the times I went there wasn't any rain. Hope this helps.
Pat