As free DLC goes.., hey wait a minute, why is this free anyway? I wouldn't hesitate to drop some MS points for Firewalker.
Let's break it down. The Mass Effect 2 DLC Firewalker gives you a handful of new missions involving a mysterious group of scientists looking for an ancient and familiar looking (for those that completed the Consort's trinket quest from ME1) artefact, and being hunted by the Geth. You get a bunch of new experience to help hit that level thirty in one play through Achievement. And best of all you get a new and awesome tank that not only hovers in four directions, but has a "boost" function to help tear up some well designed outdoor maps. Add to that an actually fun mining mini game (imagine that!), and it is a must have for any real Mass Effect fan.
The only downside (and it's not really a downside as far as this DLC is concerned) is that it makes me long for a vehicle like this in the main story. As fun as the few levels were to play through, when they are done your shiny new yank will just sit in you cargo bay gathering dust. How great would it have been to keep the old planet missions but swap out the Mako out for the M-44 Hammerhead hover tank? I would have spent hours zipping around and playing the stay-in-one-spot-while-your-tank-slides-around-randomly mining game. Oh well, maybe in Mass Effect 3 (pretty please Bioware).
If one is to take into account value for money then Firewalker should get 5/5, but then what would be the point of reviewing free DLC. I'm going to have to give it 4/5 if only because it gave me a taste of what could have be a great feature in the main story and left me wanting more.