Small, light, high flow, fast recharge, very consistent. Will feed a marker directly (no front grip reg required.)
Mounts on a standard dovetail rail.
Integrated on/off with dump (now with a lock which fixes the earlier model's tendency to degas itself at inconvenient moments.)
Easy to strip and rebuild (it takes me 5 minutes to strip, clean and reassemble.)
Regs and spares ordered from the MacDev site in Australia turns up in 2-3 days by FedEx - quicker than most UK suppliers!
Cons:
It really, REALLY doesn't like dirty air - it has a filter in the fill nipple but if dirt gets into the seat the output pressure will creep.
Pressure adjustment requires you to turn off, adjust, turn on, check, rinse, repeat. Once it's set that's no problem but it slows down initial setup slightly.
MacDev sometimes have stock problems so if you're buying one new, you'll either get it in two days or you'll have to wait several weeks.
My verdict - best adjustable reg currently available. I'm biased though - I've been a Conquest flagwaver for some time.