Fate can be fun, if you're into pure hack and slash gaming. However, it has some other problems that make me recommend against it.
First, it won't run on a non-admin account. So, if you expected to be able to install it and have your kids play it from their accounts, don't even bother to download it. I even sent an e-mail to the folks who did the Mac port, and got the following one-sentence reply: "Some guys are not designed to run on non-admin accounts."
Second, it's got some weird launch quirks like no app I've ever seen before. I can't launch it from Quicksilver or from the Recent Items menu. I see the Dock twitch a little, like something launched and quit before it could fully appear on the Dock, and then nothing. This concerns me a bit, mostly because I wonder, as a developer, how the heck they managed to make it do that! (It does this on two machines that I tested it on, so it's not a problem with the machine.)
Finally, it's got some crash problems. In the short time I've had it, it has quit unexpectedly once and the sound degenerated to static and squeals once until I quit the game.