I'm much more confident in the low light focusing - I got shots before w/ the k5, but the k5iis is just a big step up in reliability and speed. Of course the sharpness is great, but the focusing is the key for me. The k5 is an amazing camera, no doubt. But the k5iis is a significant improvement... if you shoot low light, seriously consider the k5ii(s)!
Here's some snaps f/ a few get togethers...
Settings: 1/100 ƒ/2 ISO 3200 55 mm
Settings: 1/125 ƒ/3.2 ISO 12800 77 mm
Settings: 1/125 ƒ/2 ISO 3200 77 mm
Settings: 1/100 ƒ/2.2 ISO 3200 55 mm
Settings: 1/100 ƒ/2.5 ISO 800 55 mm