Originally posted by Des I'm so pleased to hear someone say this out loud. To admit that the inconvenience of a manual aperture lens is sufficient reason to pass them by has seemed to me profoundly uncool. It suggests the sins of disloyalty (a denial of the great Pentax heritage), profligacy (willing to pay more for ease of use) and dilettantism (I'm not prepared to take the trouble of setting lens aperture manually, so I'm not serious about photography).
It's not so much the inconvenience for me, it's more a question of accuracy. For a long time, I shot with nothing but M series lenses in manual mode on film bodies, and I enjoyed it. After going digital, I did a LOT of shooting with an M series 100mm macro on my K200D. Green button exposure was unreliable. Metering via DOF preview and manually setting exposure worked, but it was a fiddly - and I couldn't see the aperture setting in the viewfinder as I could with my MX. Now I've got a K30, and it doesn't support metering during DOF preview, so green button exposure is my only option with older lenses. Thankfully, I've replaced the old macro with a 100WR, but my other M series lenses see very little action these days. Maybe if they had more useful fields of view on APS-C I'd be more inclined to mess with them.
I don't mind shooting in manual exposure mode with a modern lens, but I tend to use TAv mode more often now that I've discovered it.
If Pentax would deign to decripple the K-mount, I probably wouldn't mind using older lenses. But what I do find I have trouble with is swapping around between lenses that have different capabilities. I like to get into a groove, and I get tripped up when I swap to a lens that requires me to work in a different way. I get clumsy for a while until I get back into the groove again. It's likely that this is partly because I tend to be more hurried than I used to be. I need to find a way to slow things down again.
But that's just me. I don't question the merits of someone else's approach. I was just throwing in a couple of suggestions for things the OP might want to keep in mind when considering older lenses.