That's what I did -set it to recent apps- and it kind gives you the double tap effect in a roundabout way.
If you are in the middle of an app, like using a browser, then you press once and it goes to the home screen. The 2nd tap brings up the recent apps. The S3 is so fast that if you do a quick double tap it brings recent apps up instantly (w/ the homescreen in the background). It's one of the 2 main reasons I went w/ Nova (the other being folders in the app drawer).
And if you are already on a homescreen, then pressing the home button once brings up recent apps obviously.