The Pentax K1000 like a breath of fresh air. It just goes.
The biggest gotcha is that all of the samples I've tried to use have meters well out of calibration. Many of these meters are broken but still read; no single setting of the ASA dial will work accurately for all light values.
The best samples of K1000 I've gotten read consistently, but like most 35mm cameras, require a little testing to determine the best setting of the ASA (ISO) dial for any particular film.
Shutters usually work well, although the nice one here was 2/3 of a stop fast at 1/30 (1/30 is actually 19mS or 1/52).
The all-metal Made-in-Japan versions are the nicest. They say ASAHI PENTAX, with "AOCo" engraving on the prism.
The Hong Kong and Chinese versions use a lot more plastic and may have grindy film advance levers. These cheaper versions didn't say ASAHI on the prism.
The K1000 has moderate to low vibration (recoil) when fired.
There is a marked red tick at frame 36, and the counters stops at 36, even though there is a white tick at 37.
The shutter release is super smooth. There are no notches of kinks as have modern LEICAs.