At this point there isn't a story mode or anything like that but it could be in the cards for the future as they are establishing a back story for the world and they even have a comic coming out to better flesh it out. There are a few elements in the game that hint at a possible single player mode in the future but right now everything is geared towards multiplayer. Deathmatch, Team Deathmatch, Siege Mode, and Missile Assault are the current modes.
Hawken is definitely much faster paced and requires some pretty quick reflexes compared to the older Mech Warrior titles. However strategy and tactics are key when it comes to winning because the mech classes are designed to work together instead of just everyone running around the map doing whatever they please.
I prefer it to Mech Warrior because it doesn't feel nearly as complicated when it comes to controls plus I prefer the faster pace of combat. All the mechs have a great sense of weight to them and you feel like you're actually stomping around in a big ass mech as the cockpit jerks around, your screens flicker when you take heavy damage and even begin to crack, you can hear the metal scrapping over walls if you walk too closely to something, and so much more.