My first bike was an FX and I used to say it was a hybrid of a hybrid. In that sense, it is more like a flat bar road bike. The gearing (att least on my model), however, is more like a hybrid/MTB. I ended up buying a road bike about two months after I bought the FX and haven't been on the FX since if that tells you anything. I liked the bike but it didn't end up being the best choice for what I ultimately ended up doing--doing longer and longer rides on the road. Of course, I didn't know that when I bought it. It ended up being an expensive experiment, but arguably a necessary one too.
In my opinion, the FX series is a decent choice for someone who doesn't necessarily need/want the suspension of a hybrid or the knobbier tires. If they're riding the bike mostly for fitness on decent roads or bike baths and aren't interested in riding, say, more than 30 miles at a time, then the FX would suffice. If they're interested doing longer rides or eventually building up to that, then I'd suggest a drop bar road bike instead. My biggest issue with the FX for longer rides is that my wrists and arms would get really sore. Plus, you can't get down at all in the wind. To me, that was an additional disadvantage.
Live with intention. Walk to the edge. Listen hard. Practice wellness. Play with abandon. Laugh. Choose with no regret. Continue to learn. Appreciate your friends. Do what you love. Live as if this is all there is.
--Mary Anne Radmacher