[Nizno]

I'm trying to figure out what the true benefit of counter attack is currently. As far as I can see the only benefit is you moving up to your opponent instead of them moving up to you. I guess this lets you setup who gets base to base, etc. Does this prevent the enemy from getting their charge attacks? Does it do anything other than allow you to determine how base-to-base contact is setup?

If it just allows you to determine how contact is setup, is that not pretty weak?

[Dezart Fox]

Well if your independant character has it, it allows him to get into contact when his unit is charged.
Also, if you have you marines in a line, power fist at one end, enemy chrages opposite end your fist will be out of 2", counter attack lets you move in 6" and get all your attacks, so basically it's letting you get within 2".

[Falstead]

Aye, basically as Timjim says. It lets you set up marines in an open formation to be safe from blast and template attacks, however when they are charged then can close formation and get the whole squadron, including a burried powerfist, engaged in combat with the enemy. Coupled with true grit this can make a marine squad shockingly potent in combat even when charged, particularly if they're in cover.

[JBunny]

What everyone else said is correct. I just want to add one more thing.

Your opponent will still charge you as normal. After they have done their assault move, you will then make a counter charge. This is where you will move any unbased models up to 6" to get them in base contact.

I don't know if you already knew this or not, but the wording of your posted seemed like you might be slightly confused on how it worked.

Also it does not negate your opponents charge bonus.

[Youngy]

The real benifit of the Trait - Trust Your Battle Brothers (which I am assuming this is relevent to) is the second attack. When combined with counter attack it means you can use the Marines for area denial. Spread them out and when they are charged, bring them all back in. I reckon the rule for counter allack should be changed anyway...