What's the difference between this and the old VBA and just what the hairy heck does that M stand for?!
a better post by SL.Improved Core, decreases the minimum cpu required slightly.
Improved (and more work to be done yet) audio core, fixes audio artifacts in GBC and GBA games which cause popping and crackling.
Improved Controller settings, allows you to assign multiple buttons.
Additional patch type supports (UPS for Mother3 GBA)
Improved RTC, and save type support.
Added MBC-7 support (basic), allows games to run and save, but does not use the correct save size.
Various game control/sound/core timing faults
Load Savestates without overwriting the previous battery
Kega plugin support, allows support for additional plugins made in the kega format, without having to recompile the emulator.
What can't/won't be fixed
Mode7 port corruption, titles in include Iridion, FF4, FF6,
The corruption is accurate emulation, so is the heavy slowdown on the map screens.
Theres others, though i can't be bothered going through the svn log for them all.