I am. My brace is an Ossur Paradigm, and I'd give it a big thumbs up. Very lightweight and comfortable, to the point where I don't even notice I'm wearing it most of the time. It goes under my ski pants, on top of the Opedix leggings I use as a base layer, and I've never experienced any slippage at all. It sits above my boot, so no problems there. The folks at Ossur were extremely helpful when I bought it and I got to try on a whole bunch of different braces and wander around in them. I would definitely recommend this before you settle on a brace; it was surprising how different they felt and how immediately I knew that the Paradigm was the right one for me.
I haven't heard the greatest things about Donjoys - apparently they're very prone to slippage, and I've also heard a lot of comments about them being bulky and uncomfortable. I went with Ossur as I'd heard that they had great sport-specific braces, and they're a local company. The other brace that has a really great reputation for skiing is Townsend; I wasn't able to find a supplier here, but a couple of skiers I know with ligament instabilities have Townsend Rebels and swear by them.
My OS has advised me to wear the brace for the remainder of this season, and next if I feel like I need it. I'm not under any illusion about it protecting me from all eventualities, but I can feel the extra support it provides and I'd definitely prefer to play it safe on this one.