Hmm do you turn off the screen? Leaving it on will result in frustration for sure. Generally mine isn't buggy at all. Also have you ever used a Slow2 (AKA Teclast T51? ;) because that UI is so much worse than the DX100 that it isn't funny at all. I mean the DX100 UI isn't the best out there but hey. I really only got 2 more issues that need to be fixed and I'm pretty much happy at that point. 1. The fade in at the beginning of each track upon manually changing tracks needs to go. 2. Playlists need to automatically update and alphabetize instead of only having them show up in the order they are synced. If they fix those two then everything else is just icing on the cake for me ;).
If I read correctly you are having some issues with the player cutting the screen on by itself? When you updated to 1.2.7 did you do a factory reset? What I always do is do a factory reset which doesn't delete your music but will restore everything back to 1.2.7 factory settings. If not you are carrying over crap from the previous firmware updates which will contribute to buggy playback and possibly a slower UI. I also clear the Media Storage Process and the Music Player Process and then restart the player, letting it sit for 15 minutes to re-index everything. Should be better after that I think. Also turning off all the superfluous stuff such as WIFI, animation, haptic feedback, tilting screen, etc will help :).
You can make things even faster and smoother by rooting the device. I rooted my device with the help of Sorensiim and even messed things up quite a few times being stupid. I can honestly say this device will be hard to brick. You'd be more likely to brick it while installing a firmware update and the power goes out :P. As long as you follow the directions you are safe and the device will be even more responsive and smooth.
Regarding smoothness and ease of use; I strictly use playlists to access all of my music. It is the smoothest and fastest method to access music and this is generally universal for most DAPs out there. Feels like an ipod honestly with its smooth and sleek nature. Using this method every single track is organized and in the order I want it to be in ;). Guess I'm a control freak. I have the player screen time out on minimal but generally I turn it off manually so I don't have issues with things changing on their own unless I accidentally shut it on while in my pocket (rarely happens but does happen at times with my T1 amp attached :P).
Also I recommend everyone be careful about accidentally turning up the volume to full blast using the screen. That is an option and very dangerous lol. I blasted myself once and a friend here destroyed his NT6 Custom IEM due to it. So be careful...
Not sure if this will be useful to you but I did contribute to the DX100 Faq page which gives full details on how to properly tag your files with mp3 tag to work with the DX100 and most players (on the fly so pretty simple and fast). I also put up a guide there on how to set up your playlists via media monkey on the DX100. Works like a charm :). You'll also find Sorensiims guide here on how to root your DX100 along with some other helpful contributions from various members. Sorry for babbling on figured the more descriptive I am may help you and others.
Thank you. I poured over the FAQ: very useful. I've linked to it in the review and brought up this thread elsewhere. I think this information is helpful. I wish consumers could get such helpful stuff from the manufacturer, but that probably won't happen any time soon.
I may well try rooting the DX100 this week as I have some time between reviews. I love being part of the DX100 community and I'm learning things all the time.