It definitely has a gimmick to try and get you to pay money to not have to wait so much. The actual battles are enjoyable though. I'm DarthDomo on there.
I've considered getting it, but I've been pretty heavy into Star Wars Galaxy of Heroes recently. Haven't spent any money, but it's the first mobile game to really keep me playing for more than a week (I'm going on three months of daily play). I've heard good things about Force Arena, and would like to check it out. Maybe I'll look into it a bit more tonight.
A lot of mobile games are meant to be played like 15 minutes at a time while you're waiting for the boss or something... Too many players try to play those games too much, hence the whole mechanic to skip the waiting.
Same thing for Facebook games, but replace waiting for the buss with checking your messages or waiting for your friends to log in...