I've never been. Alysia has been several times and enjoyed it. In fact, she used to be afraid of roller coasters until she went in there and created her own coaster simulator ride. So I thank Disney Quest for that :-)
I've been in it twice or three times, but I didn't care for it all.
I think it's a ton of fun but I do agree with many on here that if it wasn't included in my ticket it can get very pricey and might not be worth the cost. We always spend our last day at DTD so we let the kids roam free at Disney Quest and they love it.