With a little more use now, I have to say I am very impressed with the M3. Scanning the 32 GB card I'm using was almost instantaneous upon its first use. Boot up speed is very quick. Battery life is decent, I'm getting about 15 hours before I recharge with a bit of battery life yet. That includes a good bit of screen use due to learning how to use and optimize the unit. The screen is good, not great. It's reasonably but not exceptionally sharp, and readability and brightness is again good but not great. Battery charging is very slow, 6 hours minimum from a low battery percentage. Those are the weakest aspects of the player, and none of them are severe or deal breakers.
Navigation is really quite easy once you use it a bit. I'm left handed but don't mind the right handed placement of the wheel. A couple of the interesting options are the slope of the digital filter and upsampling. I do notice some difference with the filter setting, finding the gradual setting to sound a little better and fuller. I haven't been able to detect any change with upsampling. Hardware and software equalizers and channel balance control are also available.
The unit is powerful and quiet. It drives Sennheiser 600 easily and well, not making the 600 sound anemic like it can when it's being driven by something that is struggling to do so. No hiss with sensitive low impedance IEM's like the FLC8S. Sound is neutral and dynamic with good extension at both ends. Bass digs deep and has good impact with natural decay. Treble is delicate and refined. Midrange is natural with outstanding resolution. Soundstage is excellent, particularly width and depth. Instrument separation is also outstanding.
I have mostly played high bit rate MP3 and WMA with some 16 bit FLAC. It handles each format well, and even high quality lossy formats are very enjoyable. In all, I'm more than satisfied with the purchase. In sure better players are out there but for the USD 200 Black Friday price, I think it's hard to beat. At full price, I think it could still be competitive but wouldn't be the clear choice, as some players have more features and capabilities. It's worth keeping in mind that this product is nearing the end of its life cycle but Shanling has continued to support and update the firmware. The firmware is very stable and mature, making the experience enjoyable and easy, something that can't always be said of DAP's.
Thanks to @nmatheis for his encouragement to buy the player. Glad I did.