I played about an hour of this today, and it's not bad. It looks like you get the whole game for free, including the unlockable characters, but you're limited in how much you can play at once. You can have up to 2 arcade tokens and 5 online tokens (They aren't called that, but there's about 17,000 different kinds of currency in this game and I can't remember their names
) at once, with one arcade token regenerating each hour and one online token each half hour. You can also win tickets that let you play for better rewards, or pay money for coins that let you play any mode. I believe these coins are the only things you can buy with actual money.
The amount of content is very limited, with only an arcade ladder and online versus matches. There's no training mode or any other way to play. The game encourages you to play online, as you get as much experience for playing one online match as you do for playing through the whole arcade ladder. I normally hate free-to-play games, but as a very casual fighting game fan, this setup works fine for me. I had some fun and got some free trophies out of it.