Get some of those old ist DS logic back! Especially 'delete all' function in the playback menu (in DS you need only to twice press DELETE button to ask it to delete all the files on the card)
Not an issue in a field use but very handy when doing test-shooting.
Also I do hope that Pentax will release a new low-latency shooting mode when shutter lag is decreased. From my measurements posted here in another thread it's clearly seen that mechanically K-5 is a pretty fast camera, but it appears to idle too much after you press the shutter release button and in-between mirror up/aperture set and shutter going toggling.
I've already met some folks who say that they do notice and feel this lag. I also assume that there will probably be some pay off with this mode - e.g. increased shutter knock sound level.
Zig