This is my favorite emulator. It's fast and does very good emulation, including sound

One of the unique features of this emulator is the Artifacting emulation. The Atari 8-bit took advantage of the limited resolution of the television to produce extra colors that weren't logically there. These colors don't show up under most emulators, so games like Hard Hat Mack, Ultima, and Pinball Construction Set end up B&W. Artifacting emulation attempts to add the colors where the logically should be. The current version artifacts with a green-purple scheme, hopefully a red-blue scheme will be added (I think this was more common on North American Ataris)

Another new feature is some of the P/M priorities have been fixed, Donkey Kong now looks correct. M.U.L.E. is still not right (The ship flys under the mountains) however.

Pros:

Has built-in monitor, Supports .XFD/.ATR files. Uses Ron Fries' Pokey emulation for sound. Built-in support for swapping disk images. PC Joystick support, Menu interface for controlling various options. Can read files from MS-DOS directories. Frame skipping has also been added for users of slower machines. Using this can lead to collision detection problems, however. This is the first Atari emulator to add artifacting support

Cons:

Some of the player/missile priorities are still wrong, although some have been fixed. There are other graphics problems (check out the field in Ball Blazer.