Hawken is a brilliant game. The sense of weight and scale is apparent. The combat, once you get the hang of it, is extremely fast based and reactionary. The biggest mechanic that a lot of reviewers seem to be missing is the Dodging / Boosting system.
You have to be quick to dodge using your boosters. Read your opponents moves and play strategically while still maintaining twitch reflex shooting. Its very, very intense. Don't treat it like your average FPS, you aren't a humanoid, you are a mech, you have separate advantages and disadvantages, get used to them. Verticality plays a huge role in the gameplay as well. The mechs are agile in a whole different way. But if you try to run and gun like an average FPS, you're toast.
There really isn't any other game like Hawken out right now. Its a Mech Sim FPS with an arcade game feel. There are 8 mechs to choose from, I think, each with their distinct advantages and abilities. The game also features a very robust item/ mech upgrade system, much time will be spend configuring the build that suits you best.
As far as the F2P model, its rather well designed, if you play smart and play well, procuring ingame credits is a breeze (as is leveling up). If you lack the patience or time, real world currency can be used for unlocks.
Did I mention the game looks incredibly stunning? No other game imo right now touts as much polish and detail visually, its remarkable that its F2P.
Get this and decide for your self.