A quick changelog since 3.0.1 includes:

• Many improvements to the texture editor:
• Extended ZDoom TEXTURES support
• Textures can be copied and pasted, including between different archives, patches and all
• Added shortcut keys and context menu for the texture list
• Added 'Texture' menu when a texture editor is open
• New 'Graphic' menu for gfx entries, with some basic gfx editing functions such as flip/mirror, rotate, colourise and colour translation
• Typing the first few characters of an item to jump to it in lists has been re-implemented
• Added the ability to open entries in separate tabs
• Dumped Audiere as the sound/midi library in windows, and swapped to SFML-audio. Upsides are much better/faster audio support and audio support in linux (and mac). Downsides are no mp3 or module format support (though I'll look into adding these back at a later date)
• Fluidsynth is now used to preview MIDI in both windows and linux
• Palettes can now be exported in various formats: raw, png image, csv and jasc palette
• Many other bugfixes and small improvements

It can be downloaded from its homepage.