Love this thing! Really... Super comfy, super well built, super spacious gear loops, and super safe. Metolius over builds every aspect of the harness to full strength specs with the exception of the rear bungee leg loops (I think) to 22KN. So you can accidentally clip your gear loop, and live to tell the tale! Seriously they do a great job, and this sucker is made in the good old U-S-A! Quality craftsmanship goes into everything Metolius makes, and it's apparent with this harness. Doubt I'll ever buy anything else for sport/trad climbing.
The twin belay loops work pretty well, and for the majority of my climbing I use them in unison. Used as such they're the same thickness of a normal BD belay loop so it's all the same to me as a user. However when rigging rappels or aid climbing they come in super handy. Having your rap set up on one side, and your personal on the other gives you a little extra play and flexibility in your set up/break down time when rapping long routes.
One caveat is that this thing doesn't have any ice clipper slots on the sides which is a huge bummer. I ice climb in the winter, and really need those. So my back up harness is a BD I've had for a few years, and only break out in the winter.
Regardless of this one small thing I would recommend this harness to anyone for any reason having to do with climbing.
I own a size Medium, and have a 32" waist with large skier thighs. She fits like a dream!