Also, a tip for those having trouble with getting Hell Raisers. Watch the cloud line, if the Geek passes below it, generally you are getting close to the ground. I manage to avoid this altogether with high rebound master and creep magnet, which in turn gets lots of ultimate smashes to power through areas. My Record right now is 372,361...
Hellraisers mostly only help you with not touching the ground or getting the atmosphere burn speed bonus (Starts at +20 when under 200 or so and gets small with going faster.). Meteor strikes will help you get forward velocity going once you're "floating" on creeps.
Still love the game despite the grinding. Some of the challenges were nice, but others are a bit tedious or require such fine reactions that you have to grind to high levels... I didn't seem to have trouble getting to the top level quickly... but I stacked collector in the beginning. I've found that if you can get through most of the Icy area without using more than 3 extra slams (regen helps with this), you can get through the last area fine.
Also, the I hate Nature achieve does involve shooting the trees at the bottom of the facility map, but you just have to do damage. I believe you get it once all the trees are shedding leaves at once... I'd be curious to take a flame thrower to it... Do this quickly with fast firing weapons with decent damage.
. Your allies in the alien campaign don't return to base right away when having captured the flag, despite the veritable lack of enemies anywhere nearby. Other things could be done for balancing, but most are minor, though the most expensive weapon in the game, the Acid Hound, severely needs an afterburn or some such, as it IS acid and the amount of hits it takes to get a kill is just ridiculous compared to most other weapons, I mean, Burrowing gun has headshots, but it doesn't?
Overall, great game, but the Alien Campaign is... bad, at best.
I gotta be honest... I love this game, mostly. Wonderful expansion of the original gameplay, but there are a few elements that need some tuning up.
AI is able to shoot faster than you are on the higher difficulty, especially in Alien Campaign. I tested it with the pistol, and it's quite obvious with other weapons as well. I understand that the Alien Campaign is supposed to be harder, but you don't make it harder by making it impossible to kill others except during reloads because they shoot fast. Granted, I don't lack in the skill it takes, I've been sniping and using the crit items throughout Quick Play and Human campaign with no trouble, but the Alien Campaign is in need of some nerfing. Additionally, it'd be nice if the Adrenaline Rush Equipment had exceptions, like headshots, crotch, butt, etc. This has also proved extremely annoying, as you must wait until the red bar catches up with the normal bar to successfully hit them sometimes.
Made some mistakes selling items and can't afford what I need to now. Have to restart, as the battles are impossible now. Don't sell items unless you're absolutely sure you can. I suffered for it.
I do not remember fancy pants being this hard, not that this is hard, but I remember being able to slide into enemies to get rid of them, now you can't really slide or hurt them by doing so... >.> <
Getting stuck on invisible things is nearly game breaking, but still, fun, somewhat challenging game, especially during those ridiculous swarm moments.
 "Synapsis 2"){kind=icon}
 "Symbiosis"){kind=icon}
 "Berzerk Ball 2"){kind=icon}
 "Raze 2"){kind=icon}
 "Legend of the Void 2"){kind=icon}
 "The Fancy Pants Adventures"){kind=icon}
 "Outpost:Haven"){kind=icon}
 "Mutilate-a-doll"){kind=icon}
 "Nuclear Plant"){kind=icon}
 "Elephant Quest"){kind=icon}