I can't speak personally to their ability to create custom orthotics, but I'm a huge fan of the shop. They are well-respected in the area as the best option for bootfitting, and my girlfriend and I have both had outstanding experiences getting fitted there. They know their stuff well, and are great about doing follow-up work after the purchase (for free, if you buy there). In fact, we're headed there tomorrow to get some tweaks to my gf's boots, which we purchased last year. She's got a wonky ankle, thanks to a previous injury, and needs to have the liner built up around it to provide stablity (in one boot). They put some pads around it last year, but now that the liner's packed out a bit, they're going to "refresh" the work to make sure she's taken care of this year, too.
The only negative I can think of, when compared to buying out west (or up north), is that it's hard to get immediate feedback and resolution on any issues. You have to drive at least 2 hours from Ski Center to get to anything resembling skiing, so it can be a multi-week process to really dial something in.
If you're going to be near a ski hill for an extended period of time, and there's a good bootfitter there, you can at least try a fix, go out and test it, and then come back to evaluate it, and repeat that cycle a few times.
Of course, if you'd rather spend your time on the big hills actually *skiing*, then maybe it makes sense to do that grunt work while you're in the DC area instead.
I hope that helps a little...