I recently picked up a heavily used K-5 IIs and am still getting to know it. The LCD has a permanent black stripe down the center of dead pixels, and some of the dials are very stiff, I imagine from the camera getting dirty. The focus screen is not centered (gonna fix that...). It's rough but lovely.
I can't tell by looking at it but it feels smaller in my hand than the K-3, and more comfortable as a result. My only complaint is the location of the back AF button, but I'll get used to that in time.
This sensor is so wonderful and produces better colors and noise than my K-3, particularly noticeable in low light.