My current bike has an Ultegra triple. I have never had the chain drop. It also has never needed anything more than a minor adjustment every now and then.

My new bike (frame's in - waiting for it to be built) is going to have a Dura Ace triple. I've only test rode the DA double, so I don't know how the triple will compare. After being used to having the extra gears of the triple I just wasn't ready to go with the double.