Hi, I'm earmonger and I'm a recovering Minidisc user....
The PCM-M10 really is your baby. It has a minidisc-like track button on the remote--along with Record, Stop and Pause. (But unlike MD, you do have to go through some post-recording clicks to actually divide at the track marks.)
A 16GB card plus 4GB built-in is 20 hours of .wav. Of course you could carry as many more microSDs as you want. (With lossy compression, you could record 320 kbps mp3 until the cows come home. )
AA batteries. (Try not to get them at gas stations, where more than once I have been gouged for dead ones.)
Ignore the built-in mics/speaker, they don't move or stick out. You can turn off all lights. The headphone out jack switches to line-out.
The hold switch does not lock the recording level, true, but there is a guard over the knob, it's a stiff knob and you'd have to work at it to move it accidentally. I haven't tried it in a tight jeans pocket, but even if you had it there, you could always put tape on it or something. I keep it on my belt in a camera pouch--I've never had any problem.
And in the pouch, if you haven't turned off the lights and leave the pouch slightly open, you can look down and see if the green light (optimum recording level) or red light (overload) is flashing, or not, near the top of the unit--(near the L and R alongside SONY). (Any problem, you can reach in and turn the volume knob if necessary.) Really, every concert I go to, people are looking at BlackBerrys, holding up cell phones, taking pix and video and generally lighting up LCDs. None of the lights on the PCM-M10 is any brighter than that.