Too bad it sucked, rate of fire was too high, it was too big and heavy as well. Generally full auto handguns have a lot of problems, and I personally consider the idea a poor one. If my handgun is my last ditch defense, I'd rather not lose a magazine with one trigger squeeze, and that is easy to do under the adrenaline dump of a firefight.
it's size and weight are an asset compared to the glock, actually. Glock 18 is 1100 rpm @ 620 grams (unloaded)
APS is 750 rpm @ 1020 grams. Sure it sucks to lug around a kilo of weight, but it would be a LOT more controllable than a glock on full-auto.
and yeah the APS is really sexy, I don't know why it's not in more games.