My only complaint with my KM is that the light metering is a bit off the wall. If you set the film speed "incorrectly" it pulls the metering back into line, the K1000 seems to be the same. Meanwhile the KX and K2 are spot on. I'm not sure if this is normal - I have seen others mention a need to adjust it this way.
The K2 also has a fairly dramatic advantage in that it offers timed exposures up to eight seconds (or up to thirty seconds in auto mode). Now, fifteen seconds and longer I can happily do with my watch and a cable release, but two or four seconds is very tricky to get spot on (and more crucial that you do, as an extra half second will count for a larger percentage of the exposure than it would with a thirty second one). I've grown to enjoy taking long exposure shots at night, or of flowing water. Both of which the K2 is much better at than a K1000 thanks to its MLU, self timer, and electronic shutter.
And before lines about "not outgrowing" and their rather strange undertone that you shouldn't have more features until you've somehow earned them come in, I can quite happily shoot with an SV and Sunny 16. I just think the K1000 is bought by a lot of people who've absorbed the idea that it's the only way to learn to take decent photos, when they'll learn just as much with a P30 and have more to spend on film.
Going back to long exposures, weirdly this is something the MV/MV1 are actually quite good at. Both have the undocumented ability to give exposures up to thirty seconds or so, and providing you're sensible with aperture settings they'll produce a very pleasing image.