I haven't had any problems with it, and someone I trust quite a bit recommended it to me.

I was going to go without when FreeTime came out, but then one of my sims got pregnant and wouldn't pop. ACR kept indicating she was pregnant, but nothing I would do would make her actually pop. I finally said to heck with it and aborted the stuck pregnancy and used InSim to speed up a new pregnancy (so she wouldn't lose any more time than she already had).