Despite my earlier comments I've been playing here and there. The moment-to-moment gameplay in this game is really good. I like the card interactions, and it's cool to see counterplay in action (even from my opponent) to inform my card choices for the following match. At one point I removed musketeer for another swarm unit, but quickly found that it was one of my strongest defenses against mid-level threats that have AoE like Witch or Dragon. Finding stuff out like that is awesome.
It is precisely the wrong business model for me to spend anything on though, because all it does it shove you into higher and higher leagues with no end in sight. The way I look at it is if I spend $20 to "get ahead" with higher leveled cards, because of the way matchmaking works, it means I'll soon meet up with people who have done the same, or have spent an equivalent amount of time on the game. So why not just stay where I am and have fun at the level I'm currently at playing for free?
I'm totally fine picking up cosmetics in F2P games, but whenever the thing they are selling is a consumable resource I tend not to play ball, because when it runs out you're just back where you started, only slightly further up the "ladder". I don't bemoan people spending money either, because I simply won't run into them – they'll be busy playing in a higher arena.
(since someone mentioned Giant Bomb) It always reminds me of when Jeff was talking about that sub-par wrestling card mobile game on the Bombcast, admitted to dropping some money in to upgrade his cards more, and immediately found himself matched against players who had also done that, so the net result was it didn't really feel any different other than the fact that money was spent. I mean, of course it has to work like that, and it'd be silly if it didn't, but unless I'm shooting for the $12000 top spot I would rather make due with what I have than pay to move up the rankings slightly.
Definitely not knocking the game itself though, it's a very well designed head to head game for sure. I found a GAF/Giantbomb hybrid clan and it's been good so far.