Ok, after reading 5 pages of opinions,
Here are what I get,
1. People want aperture level coupler, because they want "fast action shootig with their K M series lens", without need use of green button.
My thought is that How fast can you go with a manual focus lens, and How fast you can get accurate focus with manual focus lens, a button click not making any addition to already slow pace of manual focus lens.
Since dslr viewfinder are not good for fast accurate focusing, even u are fast at manual focus, today 24MP sensor will show up any little misfocus.
Forget fast action with manual lens. That is why they made dfa 70-200.
2. Ok, if you are at god speed and eye accuracy with K M lens, are they really the best among K M A F FA DFA lines.
Just for sake of K series and M series, the best K M lens are already replaced by A lens in film age, which no need green button already.
So get those A * lens instead of the cheaper K M version, they are best pentax manual focus lens.
K50 f1.2 replaced by A 50 f1.2, M* 300 f4 replaced by A300 f4 and A*300 f2.8 and so on.
So, for those asking for aperture coupler,
Naming a K series or M series lens that worth the effort.
3. Of course, someone would say, "all my k m lens are best pentax lens, like M 200mm f4, i like the render, and i care that that 1 sec green button click after focusing for 1min, because i am perfectionist."
Ok, same as I do, I use k m series all the way to the best with matte focus screen, and tired of inaccurate green button meter,
So my solution is shoot all manual mode, forget those metering process, if you already a hardcore pentax user,
You should learn shooting with manual aperture, manual shutter, iso fixed like those no-battery k1000 or mx slrs.
People old days shoot all day long without meter, and still get perfect photo with manual focus sunny 16 rules.
So shoot all manual and remember ev number of commom lighting condition. You dont have to green button if you confident your setting is all right.
4. ok, so relax, K M series are good memory of past, even the slightly more modern film lens, like F lens, FA lens, may not good enough on the coming Full Frame pentax DSLR, because of purple fringes, maybe except FA* lineups
Manual lens are good for sunny afternoon walk, but they are too old to try to do things today's young people doing,
let them enjoy retirement, let the young carry it on. use the green button, it is just like wheel chairs that help the elderly move around, or don't use it and just walk if you can manage move around without.