Hey, I am using no$gba, okay, and you know how the max speed is supposedly 200%? Well, when I set it to MHz Disaster 10%, walking outside was at 200% about, inside a building was at 220-250%, and battles are at 500-600%! Faster grinding FTW! The menu is almost too fast, though, so it can get dicey when you're trying to switch your team around. If you set it to MHz Disaster 50%, walking is 150 and battles are like 350 I think. And there's no frame skip either.
Although I'm not too clear on whether you use an emulator or not. MHz 10 is better on HG/SS since you can use the mouse for everything except moving the character around.
I typically slow it down for gym leaders, though.