The main issue for the majority of the games is that the frames per second tend to be much less than is desirable, making the game slower and choppier. Still, this application already lets you save your game at any point in time, and it supports sound and graphic rendering with OpenGL.
One of the best things about Nds4droid is that the application is open source, so any user can download it without paying anything and even change its code. Loading ROMs is exactly the same as it would be with any other emulator.
Nds4droid supports some video games but not all of them. Some work perfectly, while others have trouble running on the emulator. Final Fantasy IV, for instance, works well but with a frame rate that is lower than desirable.
Nds4droid is a Nintendo DS emulator that is powerful and comprehensive. It doesn't yet support the entire catalog of games for Nintendo DS, but you can still play a good amount of excellent titles.