The last official version of VBA GX was 2.2.8 in July 2012. This version was released March 4, 2015, and is labeled as 2.3.2.
Download: Dropbox or Mediafire
Source code is on GitHub: https://github.com/libertyernie/vba-wii
Major changes in 2.3.2:
Pokemon Silver on GBC with SGB border - stretched to full resolution (640x480):

Same game, running at 2:1 pixel ratio (512x448):

Changes in 2.3.1:
The biggest new "feature" since 2.2.8 is that for GBA games, it's now using the tiled rendering method from RetroArch. (It's also made its way to VBA-M upstream, but RetroArch had a couple of fixes I needed to apply as well.)
What this means:
That video is showing the new version - here's a video of the old version. You can kind of tell that the game's running more smoothly if you play them side by side, but it's definitely noticeable in person.
Download: Dropbox or Mediafire
Source code is on GitHub: https://github.com/libertyernie/vba-wii
Major changes in 2.3.2:
- 240p support added (NTSC and European RGB)
- Wii U Pro Controller support
- Borders of arbitrary size supported - loaded from PNG files (must be enabled in Emulation settings)
- Known issue: pixels in the border must be the same size as pixels in the game - unless you want a tiny screen you're effectively limited to about 320x240.
Pokemon Silver on GBC with SGB border - stretched to full resolution (640x480):

Same game, running at 2:1 pixel ratio (512x448):

Changes in 2.3.1:
- Super Game Boy border support
- Borders can be loaded from (and are automatically saved to) PNG files
- Any border loaded from the game itself will override the custom PNG border
- Custom palette support from 2.2.8 restored
- Option added to select Game Boy hardware (GB/SGB/GBC/auto)
- Fixed pixel ratio mode added
- Overrides zoom and aspect ratio settings
- To squish the picture so it appears correctly on a 16:9 TV, you can open
the settings.xml file and add 10 to the gbFixed/gbaFixed value. However,
setting your TV to 4:3 mode will yield a better picture.
- Real-time clock fixes for GB/GBC games, including Pokémon G/S/C
- RTC data in save file stored as little-endian
- Option added for UTC offset in the main menu (only required if you use the
same SRAM on other, time-zone-aware platforms)
- New option for selecting "sharp" or "soft" filtering settings
- "Sharp" was the default for 480p, "soft" was the default for 480i
- VBA-M core updated to r1231
- Tiled rendering used for GBA games (new VBA-M feature, originally from RetroArch) - provides a major speed boost!
- I merged the changes from cebolleto's version (http://gbatemp.net/threads/snes9xgx-fceugx-and-vbagx-with-screenshots-support.366990/). See that thread for details.
- New options available:
- Disable the " Auto" string being appended to save files
- Disable frameskip entirely on GBA (I like to turn this on in some games and keep it off in others.)
- Keyboard fixed (from libwiigui r56)
- GUI prompt is now purple instead of green (button colors more intuitive)
- Goomba and Goomba Color ROM support (using my code from here: http://gbatemp.net/threads/goomba-save-manager-export-replace-goomba-sram.364693/)
- Any Game Boy ROM stored within a Goomba ROM can be loaded "natively" in the Game Boy (Color) emulator (or the Goomba ROM can be loaded as GBA)
- Game Boy SRAM stored within Goomba SRAM is loaded and saved correctly
- I put this in because I keep several GBC games on by GBA flash card, and I like to use the same save file no matter what device I'm using.
- Custom controls available for Kid Dracula (see this video)
The biggest new "feature" since 2.2.8 is that for GBA games, it's now using the tiled rendering method from RetroArch. (It's also made its way to VBA-M upstream, but RetroArch had a couple of fixes I needed to apply as well.)
What this means:
- GBA games are going to run a lot more smoothly. (They'll usually still have some frameskip, though.)
- If you're already using RetroArch to play GBA games, just keep doing that - this probably won't help you, unless you need something specific that VBA GX has.
That video is showing the new version - here's a video of the old version. You can kind of tell that the game's running more smoothly if you play them side by side, but it's definitely noticeable in person.