No program is without it's share of bugs, here are the notable (known) ones for MeBoy, as of version 2.0:
- Some games are not drawn correctly, in particular some graphics that should be "in front of" other graphics are instead drawn behind. This is generally the result of certain shortcuts used to speed up emulation by sacrificing accuracy. (This issue does not exist when using the "Advanced graphics" setting, but on the other hand that mode is too slow for many phones.)
- MeBoy does not support multiplayer games (using the link cable).
- If you force-quit MeBoy (for instance by holding down the "back" or "hang up" button), MeBoy will not save your progress, and your savegames can revert to a previous version. To properly exit MeBoy, select "Exit [game]" in the in-game menu, and then "Exit" in the main MeBoy menu.
- MeBoy currently does not support Gameboy Advance games. The Gameboy Advance is a completely different architecture from the Gameboy and Gameboy Color, and has much higher performance demands.
- Some games will not run. There is an incomplete compatibility list for MeBoy, and the list for JavaBoy can be found here. Most games will either work with both or neither emulator, but there are exceptions.
- Some Sony Ericsson phones (including K700i) will misinterpret button presses when the joystick is held in some direction. This means only buttons 5, 7 and 9 can be reliably used together with the joystick, and the other buttons work "sometimes". (This is not really a MeBoy issue per se, but it is a limitation when playing Gameboy games.)
- For Bluetooth-related issues, see the Bluetooth Guide's troubleshooting section.
The primary reason MeBoy is slower than most Gameboy emulators for Symbian phones is that it's an emulator (for Gameboy) inside an emulator (for Java). There is a lot of overhead in each step, and MeBoy can only control and optimize the Gameboy-to-Java step. (On the flip side, using Java means MeBoy can run on non-Symbian phones.)
MeBoy has a performance issue with games fading the screen, since this wreaks havoc on the image drawing code. (This issue does not exist when using the "Advanced graphics" setting, but on the other hand that mode is too slow for many phones.) Emulating the Gameboy Color is also much more demanding than the regular Gameboy, because the Gameboy Color has a much faster CPU, and also larger RAM and of course a more advanced graphics chip. Games fading the screen are also much more common on Gameboy Color.