Didn't see another better place to post this, so I will here:
Well, a lot of the problems have been gone over already. I'm shocked that they weren't picked up on by anyone in the studio. I'll do a little summary and add some thoughts of my own:
The DLC name is stupid

Firewalker? Really? Then why do I blow up in 2 seconds when I get anywhere near fire? The sensors inside the Hammerhead are so advanced they think its a good idea to just sink into burning hot lava? Surely the dramatic increase in temperature would have said 'oh ****, don't lower any more' long before you actually hit it? NO? Disregarding lore and common sense, its never properly explained to the player that lava and acid (?) lakes are massively hazzardous. I had to actually explicitly test whether or not it would do any damage to me at the end of the first (training) mission. Which of course killed me, sending me right back to the begining of the mission. *sigh*
If anything, the HammerHead is more like a Rockhopper or something than a firewalker.
Control is actually ok.

Pretty intuitive controls. Responsive, most of the time.
Driving is kinda fun.

The funnest moments in the firewalker pack was when I was just boosting along at ground level, coming to a gap, and jumping up over the gap. There should have been more of that, rather than having to strafe around (or worse, and actually more efficient, just standing still) and shoot enemies.
But its not great <_<
Cornering causes a bit of a stall in speed it seems, but with no indication as to why. Like, it has to come to a complete stop, turn, then accelerate. Thats not how it actually operates, I know, but thats how it feels when the camera lurches towards the rear arse of your craft every time you turn. Crashing into things, just stops you, with little penalty. Theres very little finnesing of the controls to be done. Point. BOOST. hop! Done.
Also, this vehicle is suppose to be able to fly. Why does boosting stop my jump recharge? Its really lame. Kinda kills the fun sometimes.
Make your minds up: Do you want a vehicle that is fast and furious and explosive, or one that is more considered and more precise. Because project Firewalker seems to by trying to be both, and fails at both.
Combat is rubbish:

Complaints against ME1 foot combat (listed in Cristina's presentation) was that it was just turned into a spam fest and that you couldn't aim properly? Well, you've just done worse. Not only is it a spam fest (infinite, rapid firing, homing, rockets? my god), you (as the player) are not even allowed to aim. It would seem natural that the selected target is where your rockets will go to (as thats exactly how powers work when you're on foot), but no, the game knows best! It is INCREDIBLY frustrating to be firing at an enemy for some time, realise zero damage is being done, then realise your rockets are trying to hit another 'more important' enemy, but because of the turning circle of the rockets and the angle of fire (which is straight at the enemy i'm trying to hit) not a single rocket is managing to find any target. This happened multiple times in each level. Apparently this is how the missile launcher heavy weapon works too. I didn't even realise, but no wonder I dropped that thing like a ton of bricks after a few shots.
Its a terrible weapon.
I'm not gonna tell you how you should change it, just that it does need changing.
With the shooting ad nausem, and the little jerk of the camera it does every time you fire, its a little well, nausiating after a while. Especially when that seems to be the most effective and easiest strategy.
Huh? I'm getting damaged?

The indication of when you're recieving damage is rubbish. No shield/armour/health indicator? All we're given is fine/on fire/dead as a status. And when you can go through those statuses within a few of seconds, with no hint of cover in the level, you're at a high risk of getting ****ed. Yes, you can go from alive to dead very quickly on foot too, but at least you have plentiful cover, powers to heal you back up quickly, and a better indicator of what your health is like!
Among the worst offender for this is the death pits (which, btw, since boosting stops your jump recharge can be a real pain in the ass when you're stuck, out over one and you're out of jump)
Am I mining or is this some kind of hovertank dance?

Seriously? Whats with that? For the most part is just; park, press and hold, profit. Whats with the shaking? The very rare occurance that you do end up getting shaken out of the circle just becomes an annoyance. What exactly is happening when I do this? Some sort of weird vaccum cleaner? Its all in random directions as well as being able to change its random direction very quickly, so if you do try and compensate for it, you can quite easily send yourself out of the circle, so in the end its just easier not to bother.
Environment design for exploration is bollocks:

Don't give me this fast, agile, high jumping vehicle, then put INVISIBLE DAMN WALLS everywhere. Seriously, seriously lame design when a good portion of the levels are based on platform jumping and scaling, even encouraging exploration to get to some alternate routes, and when you try and go to a ledge that is perfectly in the HH's range, there's an invisible wall in the way. A player encountering an invisible wall at any time, at any point in the game, for any reason is a failure of design and test. Its immersion breaking, poor quality, fun destroying, frustrating and makes the world feel much smaller instantly. Similarly, creating geometry that isn't actually... 'real' is equally as stupid.
Good example: in the lava mission (where M-44 is on a random rock at the start) turn around and jump straight up the wall behind you. You'll not only be able to get to the height, but even land on the ledge. Except, theres an invisble wall blocking any further progress. Better still, in another mission (I forget the exact one, I was more keen to get to the actual gameplay) I actually hit the bloody invisible ceiling, while going over a jump it seemed you were supposed to!
Very little in the way of actual, play time:

Taken together they're maybe 3/4 hour's worth of content at best. And thats being generous. Very little in my 30-50 ME2 experience. For the flagship player controlled vehicle of ME2, this is a very poor introduction to it. If this anything but a minor test and feedback gleen, you've wasted your time with this thing. Its entirely skippable.