Full changelog:
Changes from firmware version 2.1 to 3.0 include the following

1.All new UI supporting new features, with orange, yellow, purple, blue, green and black color themes.
2.Support for DSD playback (supports DSF and DFF files in DSD64 (2.8MHz) format. Does not support DSD128 (5.6MHz) format or ISO files.)
3.Increased responsiveness to track changes.
4.Increased speed of media library update, added song no. progress display.
5.Added support for HE-AAC format.
7.Added support for cue sheets for mp3 tracks.
8.Added large charging indicator on LCD screen when charging with power off; screen shuts off after the pre-set screen timeout.
9.Lifted restriction on playback of tracks of sample rate under 32kHz.
10.Added display of number of songs on TF card and internal storage in “About X3”.

Bug fixes and improvements:

1.Optimized mp3, wma, ogg vorbis and flac decoding quality (fixed noise artifacts in left channel of ogg vorbis tracks and low level noise in mp3 tracks)
2.Fixed issue where flac tracks split by CUE files were not split at the correct track positions.
3.Reduced gaps in gapless playback (zero gap in tracks of the same sample rate) (not applicable to “shuffle” or “loop single” playback modes or tracks split by cue sheets)
4.Improved support for ID3 tags and album art (lifted restriction on size of album art)
5.Improved support for different CUE sheet formats (added support for UTF-8 and Unicode files)
6.Added support for 32bit, 64bit and floating point music tracks.
7.Increased responsiveness to fast forward and rewind operations.
8.Added large charging indicator on LCD screen when charging with power off; screen shuts off after the pre-set screen timeout.
9.Various bug fixes.