You might try one of the previous versions of Linux Mint with the Cinnamon or Gnome desktop. Depending upon how much memory your machine has you might like that OS much better.That's not a bad idea to salvage some life out of an old Mac, but I seriously doubt your average user is going to prefer any flavor of Linux over OS-X. Much as I rag on Apple for their overpriced products and their base of slavishly devoted, often irrational, fan-boys, they do have a really polished and nice OS.
You’d be surprised. The modern Gnome desktop, and the new Cinnamon are pointed more towards the eye-candy crowd, and I have indeed steered some clients away from the default mac OS’s they normally run and over to Linux because of the way the two desktops look. Plus, they really are for the most part plug-and-play, or turn-on-and-go, if you want to get literal about it.
Not to mention it’s all free along with the newer versions and security upgrades. Add to the fact that OS-X is a ‘nix-based OS and many versions of Linux are quite similar to what they already are familiar with on their machines. :)