Time to give you some feedback.
I tested Gameyob with a couple of games and found a few errors to report.
This is tested using the latest Gameyob build as of March 19th 2013 at 11:15am (GMT) with a GBC bios running, and Lameboy 0.12.
Tetris DX - Works perfectly, except that the background colour does not update when you achieve certain levels.
Starting a game on level 0-4 will give you a yellow background, and level 5-9 gives you a purple background. Every 5 levels the background colour is supposed to change to the next, going from yellow, to purple, then cyan, green, grey, black and finally blue.
Lameboy does this correctly. Alternatively if you load a save-game in progress, it will load it with the correct colour background (E.G. green during level 17), but it won't update when it's supposed to.
Konami GB Collection Vol. 1 - Boots fine, when you get to the game selection, the game does not let you press up or down to select one of the four games, only the first game is playable: Gradius.
Lameboy can play this properly.
Konami GB Collection Vol. 2 - White screens after the GBC bios Gameboy logo animation.
Lameboy can play this properly.
Konami GB Collection Vol. 3 - Appears to have no faults in loading or selecting a game, same with Lameboy.
Konami GB Collection Vol. 4 - Same as Vol. 2, white screens after the GBC bios Gameboy Logo aimation.
Lameboy can play this properly too.
I've tried other stuff too, the translation patch for "For the Frog the Bell Tolls" seems to be working perfectly, Shantae seems to run fine but just slowly, and slower than Lameboy.
Hope there was something of use here.