I had an Atari 2600 clone as a kid but never owned anything else Atari until a few years ago when a flat mate of mine told me his work was throwing out an Amiga. He couldn't tell me what kind but I turned up at his work to pick it up.
It turned out to be an Atari 1040 with 4Megs of ram, the monochrome monitor and the cubase cartridge but no software. I thought what the heck, I have always been interested in what was so great about the Atari after a few of the typical playground arguments and took it home to play with.
Games seemed OK. Some were on par with the AMiga versions, some worse some better. I also liked the fact that it had the RAM expansion on the motherboard which took normal, for the time, RAM which I felt the Amiga could have always dealt with. From what I could see, cubase looked pretty good as well and I can see how this application helped to sell a number of Atari units.
As for their desktop GUI, GEM, I personally found that to be a major let down. 3 screen modes, the 2 lower res ones supported colour, the high res one black and white. The only way I could access all of them without a special monitor was to have the monochrome monitor plugged into the monitor port and a TV set into the RF port. I found the GEM interface pretty bad to use and work with, it reminded me of early MacOS and it's single tasking.