The Flow EX rim looks much better than the Flow for big tires and heavy use. It looks like a perfect burly AM rim and may make a good DH rim but I'd still like thicker sidewalls to withstand dents and another millimeter or two of internal width would be nice. It's only 490g (20g more than Flow) so another 30g+ of beefiness would still make a very light DH rim.
Here's hoping a NoTubes DH rim is around the corner.