In reply to Dave Reeve:
We've had the Ohm for a few months and are still getting used to it. The following is from a belayer's perspective - I've never tried leading with one myself as my climbing partners tend to be heavier than me.
I'm a lot lighter than my partner, and even with the Ohm I tend to be pulled up about a foot if he falls (i.e. twice the length of the QD the ohm is attached to). Keeps the catch fairly soft, though not as soft as when I used to be pulled up several feet.
Not had the problem with jamming round an acute angle - but then I don't tend to belay from a long way back.
Our main gripe is that it's a fiddle to unlock after a fall, and this can particularly be a pain when my partner is trying the same hard move several times.