Dolphin, the GC/Wii emulator named after the GC's internal development name, hit a milestone today. 4.0.1 is considered stable enough to release and has quite a number of changes. In addition to coming in an installed format and using the user's documents folder (opposed to running standalone from whatever folder the user dumps it in and reading config files relatively), the DSP HLE code has been rewritten and the changes have been merged.
Audio bug fixing is likely to be very welcome for some games, as we've seen time and time again in emulation that audio emulation is not limited to just the noise that comes out of your PC speakers and can heavily affect game compatibility.Dolphin 4.0 introduces a full rewrite of the audio emulation used in 99% of games, fixing hundreds of audio related bugs in Dolphin. On the flip side, it is now required to run a game at full speed to get full speed audio out of it, which is a direct consequence of fixing these bugs.
Those aren't the only major changes, however. Something new, and this one came out of left field, is beta support for the Wii official online multiplayer. That's right, the main branch now supports games like Mario Kart Wii and Super Smash Bros Brawl online. There's other changes as well, check out the source for the full list.