I've been using a Pentax Optio 555 myself and I like it with its 5mp resolution and its 5x optical zoom lens. And it seems to do pretty well with shutter lag - that is, the lag doesn't seem to be much of a problem, but I'd like to see all cameras made with no lag whatsoever, or lag that is so slight, that it effectively isn't noticed.
The Pentax Optio 555 is fairly small for what it offers, but I wouldn't necessarily call it pocketable. Pentax is going to be releasing their new Optio SV, which also offers 5mp resolution and a 5x optical zoom, a 1.8" LCD and its dimensions are only 92mm x 56mm x 28mm, which is pocketable. The Optio line all take SD cards.
DP Review has some info on it
Click Here - Optio SV
Of course, I have no idea if there's much shutter lag on the SV camera, but my guess is that it's most likely very little... Pentax has been workin' their Optio line for sometime now, working out all the kinks. I've been happy with the 555, but would love to have something smaller, like the SV.
The problem with going with something really pocketable, is that the sensors sometimes are not as good as what's in their slightly larger cameras like the 555, resulting in quality that isn't quite as good as one would expect. I suppose it shouldn't make a huge difference, but I've noticed in the past that there is some difference. I'm hoping that the SV wouldn't succumb to this problem.
What Casio has been putting out looks pretty nice as well. So I think your best bet with an SD-based pocketable camera in terms of balancing size, features, resolution, optical zoom, speed, and photo quality, is either Pentax SV or Casio Exilim.
And yes, I would agree, most manufacturers don't list shutter lag specs. You just don't know until you're holding the camera in your hands.