A check from one of those Free XBox offers was waiting for me when I got back to school.
The biggest problems I had were that I forgot to cancel a $1/day offer and got charged $40 (which was overturned by a call to their customer service) and cancelling AOL (something I just did a few weeks ago). They sure were persistent in trying to get me to keep their service. The other 3 offers I signed up for (eFax, Blockbuster Online and Real Rhapsody) were free 2-week trials and were cancellable online.
Needless to say, giving away free stuff is not a very healthy business model. I-Deal Direct (the company that runs this program and others like it) is starting to crack down on people who are doing more than one of these deals. They've increased the number of offers one needs to sign up for and they've also increased the time one must wait between signing up for offers from the same advertiser from 90 days to 6 months.
It did take me three months, and there were a couple of bumps in the road, but all in all I'd say it was worth it. I don't know if I'd be able to say that if I started the process now, but there's very little to lose in trying. It would probably be wise to look at some "guide" sites that suggest which offers are the best to sign up for.