I have no desire to use the K-1 or any DSLR for that matter, I have moved on to mirrorless or medium format. The 5D kit sits unused, the L series lenses now mainly used on the video camera or the A7. Working for the local Pentax distributor means I have access to a K-1 and have been shooting the beastie for about four weeks.
My first impressions were that it was a capable and well put together camera with an over complicated menu system and more features than just about any other camera. To be fair on the menu system, it is better than the Sony but that is not hard and the features are many but for me most of them are left unused.
The proof that this camera has potential came firstly with some landscape shots I did on Lake George. I was shoot the H6D as well as the K-1 and on seeing the results in Lightroom was pleasantly surprised- nowhere near the latitude and tonal range of the H6 but the detail and resolving power of the 36mp sensor and the Sigma 35mm Art was good, possibly exceptional for a DSLR.
So I continued with the K-1 Sigma combo and found a great landscape camera but also a pretty neat street shooter as well but the real party trick for the K-1 is the ability to use ALL the old K mount lenses. I dug out my K1000 and whacked the 50mm 1.7 on it- works perfectly.
So now I am on the hunt for K mount glass and there seems to be a bit out there at really reasonable pricing.
If you are looking for exotic glass Cosina made K mount glass as Cosina, Voightlander and Zeiss that was excellent. Sigma and Tamron still make some K mount with the 35mm Art from Sigma a standout. I have tested some older zooms and they are best avoided, Pentax zooms were never that good so keep to fixed lenses.
The K-1 was a surprise and is turning out to be a lot of fun but also delivers excellent results and has so many features that I keep discovering a new way to use it every time I pick it up.