Originally posted by pathdoc I know this is going off topic, but I'd be interested to know what those were. I have accumulated quite a few Pentax K-mount bodies, all of which do things in a somewhat different way (except for the second Spotmatic, which came free with a lens I wanted and may yet go to charity with a lens I don't want).
1) fully automatic film loading; 2) motorized film advance; 3) spot, average and simple zone ("matrix") metering quickly selected via a sliding switch; 4) built-in intervalometer for automatic shooting of an entire roll with intershot delay adjustable from about one second to a several hours. 5) electronic rather than mechanical cable release (although I have come to wish all modern DSLR's had a steel shutter release button threaded for mechanical cable releases) 6) a very clever, tiny, convenient clip-on TTL flash. 7) full information in the viewfinder (meter pattern, f-stop, shutter speed, exposure adjust, flash ready, flash exposure confirmation).
No Pentax body at that time offered these features. To get motorized film advance, you almost always needed a separately purchased winder. I had the winder for my LX, but when attached, it made the camera body clumsy in the hands, less stable on a tripod and It was nothing like as convenient or quick as the built-in film advance of the XR-M. And when did Pentax introduce a body with multiple metering patterns? The X synch on the LX was dismally slow (as I remember, on the XR-M it was 1/125, a full stop faster).