I scored a package of 28mm 2.8, 50mm 1.4, 135mm 3.5 and 200mm M's on eBay and I love them. Sold off the 50mm due to redundancies with A's and FA's but all the others are happily with me. I hate it when I succumb to laziness and opt for the easy way out using the DA zooms.
When I first went to Pentax digital it was because I had a few screw-mounts that I really treasured, but I found stopping the lens down manually was more of an effort than I wanted. The M's, however, are just the right level of old-school to make me take a second to think about what I'm shooting.
Another boring old goose photo, but I liked the light.