Usage and Sound Quality
I wear the M3 through most of every work day. I keep the remote clipped to my pants pocket, on the outside when I'm at my desk, and on the inside when I'm working in the warehouse. (I've still scratched it a bit.) I run the headphone cord under my shirt usually, as all the wires do cause problems sometimes, and can grab doorknobs or other projections as you pass by. I can use it for 2-3 long days before I start to get low on the battery.
Adding files is a snap. When you plug in the M3 to the USB, it shows up as an external hard drive. You just drag files and folders into the drive and they are ready to play. I have not yet come across any file that it could not play, and though some on the forums talk about crashes and resets, I have experienced none. The M3 can also be used as a external drive, and you can store any file you like it. The player comes with an interface program for converting to mp3 and adding music to the player, but I found it useless and have not used it. My only complaint is that when the player is connected to the USB port, you cannot play through the headphones. You also lose your place in your current track, so if you want to start back where you were after connecting to a computer, you'd better bookmark!
Sound quality is fantastic. I'm no audiophile and anything higher than FM quality sounds good to me, but the sound from the M3 is consistently clear and strong. It has quite a lot of equalizer options and settings and to be honest I've hardly looked at them.
Many players have problems transitioning from track to track and you can get quite a gap (up to a second) between songs. The M3 has an almost imperceptable gap, though it is definitely there. When you play a continuous album, like a live recording, you can hear a small space between tracks, but it can't be more than a 10th of a second. It's not seamless but it's close.
Start up takes a moderately long time, perhaps 10 seconds. When you pause for a while the M3 automatically shuts down, so then you have to reboot when you want to listen again. However, the M3 can be set to autoplay when it starts up, so you can stick the remote back in your pocket once you've powered up.
I have also been surprised to find that I use the player without the remote more than I thought I would. I listen to a lot of audio books, and once they are going all you need is pause and play. I listen while I'm cleaning up at night and don't bother with the remote, just for simplicity. The buttons on the player feel good and respond well. Though they don't have any special texture, it is easy to tell which is which without looking.