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Using this rope with a gri-gri would be a gamble. The gri gri is rated for ropes that are 10-11 mm in diameter. This being 9.8 is close but...The mechanism in the gri-gri depends on the diameter of the rope being at least 10 mm for an effective stop..This rope is sweet and I would highly recommend it...I also have a gri gri and after using it a few times went right back to a normal ATC....Having a gri gri is nice when you are climbing with someone who isn't an experienced belay (or a friend you know doesn't like to pay attention) because it has the auto lock feature but atc's are way more versatile and my climbing life has become way less complicated since I switched back.

If you have the cash to spare the XTR is definitely worth the price and performs better than XT components. With that said, components break and you have to replace them. The choice is yours...

10-11mm

It is machine washable but it'd be a good idea to avoid the dryer. Heres some more info on patagonia.
http://www.patagonia.com/web/us/patagonia.go?assetid=8514

You can definitely fit a sleeping bag in there when it's stuffed but the bag doesn't have an actual designated sleeping bag compartment.

I agree that this beacon is pretty good. Pretty much all beacons have both transmit and receive ('locate'). However, this isn't a PLB (locator beacon) which alerts rescue teams to come find you. Its intent is to find someone within very short range (~30m) under avalanche debris. Also, keep in mind that if you're depending on rescuers to find your son, you're thinking the wrong way. Rescuers take hours just to arrive on scene, suffocation under avalanche debris takes minutes. Proper beacon use, irregardless of -which- beacon depends on education and trained ski partners, who, by virtue of skiing with you, will be there on scene (with their own beacons) hopefully in time to do something. Beacons have less than a 50% live find rate for recreational skiers. Almost better to spend the $300 to take a class, learn the basics, and rent a beacon instead.