I took my family last year, mainly because it was right in our backyard (30 min drive). We had a blast even though it was nearly 100 deg all 3 days.
Positives were the trail rides, new Jeep off-road course, engineering roundtable, the fact that they had activities that my wife and kids found interesting, and the most incredible fireworks show I've ever seen.
Negatives were some of the activities filled up very early, the concert (Jason Mraz) sucked, and on Sunday they opened it up to the public and held a mountain bike race at the site. By 11am traffic was backed up for miles and the place was packed with "public" who had free and equal access to all the activities (except trail rides) that we paid for. Oh yeah, they made this announcement about opening to the public AFTER the time when you could get a refund.
That kind of ruined it a bit, but overall it was fun and if it were closer, we'd probably be going back. I wonder if attendance is down this year because they sent me a letter offering me $75 worth of gas if I signed up.
Have fun and be sure to post some pics for those of us who can't be there.