Yeah, this game is fun, intense, and addictive. The aforementioned 5 minute game length also makes it a good game to hop in and out of if your time is limited. It is just a matter of whether you have the willpower to quit after one game. Or two, or three, etc. There have been multiple times when I have turned on the PS4 intending to play something else, decide to have a quick game of RL first, and never end up playing the game I originally meant to play.
Also, I read a quote somewhere from the developers about the PS+ deal. They had no intention of having it show up on PS+. Sony came to them with an offer and they turned it down. Soon after that, Sony came back with "an offer we couldn't refuse." Developers are paid per download for PS+ titles, so I imagine they are getting good money from this, plus it got their game in front of millions of gamers that may not have given it a chance if it wasn't free. I am one of those people. I wouldn't have paid $20 for it before I played it, but now that I have, I feel it is a good value at that price point. I plan on throwing 4 bucks at them for the DLC just to further support the developers, and I am sure many other PS+ users will feel the same way.