I like having two wheels. It's part of the value of having an advanced user camera (hope that's PC enough
) to have more controls and settings on the outside of the camera body. Many people may not use the m..manual setting, but one of the reasons I got my K-5 and K10D...is to fully use every part of the camera.
I maybe different, using a hand held light meter occasionally, but let me tell you it's a wonderful part of photography for me to do my own metering.
My first good camera, the Pentax S1a, did not have an in camera light meter. That was back in the 1960's so I had to learn to use a separate meter and I also carried around a gray card...still do, in fact. In the '70's and '80's I got some medium format cameras. A Zeiss Ikon Super Ikonta B and a Mamiya 220 Pro F, twin lens reflex and also a Leica 35mm Rangefinder. All these cameras did not have an in camera meter...so metering became and is second nature.
But with hand held metering, you need to be able to precisely control your shutter speed and F stop. For that you need full functioning setting ability, which with two wheels, set on M...is quite easy to do.
To me it's great to meter, then set, then check exposure with the monitor image...then try a number of different settings of F stop/shutter speed..if you want....all as dictated by the hand held meter. My meters...give a plethora of settings...which I love to see and use if I choose...to experiment .
Excuse my long windedness....but a K10D, K-5...advanced camera gives me that ability. I also set them on aperture priority an awful lot too. But I do like to meter with a good hand held meter.
My favourite hand held meter, is my new Sekonic L-398 Studio Deluxe lll. I've got three light meters, including the meter I bought back in 1968. It's a Sekonic L-248 and it still works.