I work in a store with a D7000 demo (cameras department ;D), and I've brought my K-5 to work several times.
-the D7000 is significantly taller than the K-5
-the K-5 feels infinitely better in hand with the more rubberized grip; it simply melts into your hand, whereas the D7000 feels a bit more unnatural to hold (to me, anyways)
-the ISO button is not in a damn illogical place, or the metering, as it is on the D7000
-the shutter sound is actually significantly quieter than the D7000. My co-worker and I were fooling around; he was rattling off shots with the D7000 and I with my K-5. My K-5 was only barely audible over the sound of the D7000.
-for some reason, I feel like our demo D7000 is a bit slow in AF, but it's quite lensdependant so I won't mention much on it. However, with our demo 50/1.4 (I take it out of the cage now and then when it's really slow
) I have to say - it's some damn good accuracy. The D7000 just about never missed AF wide open, even on moving subjects. I think the K-5 is a shade faster though, even with my FA43 (which is supposedly slower than most DAs)
-they both weigh approximately the same (though just going by feeling here), but due to the (very noticeably) smaller size, the K-5 feels a lot denser, a lot more solid
-the K-5 isn't quite as sensitive as the D7000's shutter button, but not sluggish either. About average, I'd say
-for the battery grip question, I wouldn't know, as I've never held a D7000 + BG. for the K-5 though, it feels quite nice in hand, and if you have larger hands and your pinky curls, it would solve the problem quite nicely while still being not too large - K-5 with BG is only a bit taller than D7000 without (which would be once again much taller if you put a BG on it).
Hope that helps! (: