I got a Medium Zephir, I usually wear a M Petzl Sama - I have 30" waist, 140lb 5'8" lean guy.
1. God, it is light.
2. It is surprisingly comfortable for the width of loops and lack of padding.
1. The leg loops do ride quite high into the crotch area (mentioned by other review). I extended the elastic strings at the back to max, and it still held the leg loops up against my other 'chalk bag'.
2. The leg loops are very narrow on the inside of the thigh, but oddly, very wide on the outside of the thigh where there isn't much pressure - added to discomfort slightly.
3. The fit was weird for me. The waist loop end 'slips' into a sleeve to keep things together, but it didn't really fit together for me, and it just bunched up. Maybe it would be different if I got a large.
4. The 'dyneema' connecting the leg loops to the belay loop is very narrow! I guess I trust them... but err... jesus they are narrow! and its thinner than a dyneema sling (but wider).
5. The belay loop is pretty small, as are the two points for rope tie in. I'm not sure I'd fit two twins in there + my PAS (and my second PAS! b/c I like to lobster claw). I'm not sure there's a lot of work area here for long climbs, or multipitch.
6. The rear gearloops are like vestigial structures... They might as well just fall off. And the front gear loops are pretty far back. They also flop around and aren't held out from the body. I haven't racked gear on the harness, but I imagine, it wouldn't be as easy as the BD's moulded gear loops.
Summary: Overall, it is a very full-featured super-light harness. It would be a contender for alpine situations where I want fast and light, but also want to rack some gear - I feel like the Petzl Hirundos would be in the same class. I would avoid this harness for gym, sport, multipitch, big-wall or trad. It sacrifices too much on the belay loop size, comfort, and racking.