No. I use juice defender ultimate. It works pretty good. Also Tasker works but is more complicated to setup. I miss smart actions. These other phone manufacturers need to take note. Its a excellent app.
What's it for? Based on what I can surmise from these posts, it's something to end tasks after a little while and help save battery power?
In the small amount of time playing with and setting up my friend's AT&T S4, it does tend to keep a lot of things open. Though I'm not sure if them being in that list is only holding onto RAM or if it's actively processing them still. There's really no way I could tell, maybe someone knows?
Smart actions can help with closing running programs but it does so much more. For instance when I put my Razr in my car dock smart actions automatically turns the GPS on, opens the nav and automatically sends a reply text that I am driving and will get back to them when I receive a text. At night I have it set to dim my display, turn off the sound and only ring for emergency contacts. You can customize it to do so many things that I would really miss it switching to another phone.