Well, it turns out that if you use it *three times* in a row doing nothing else, it applies a tiny damage resistance debuff against *slashing damage only*. That's not even all of *your* attacks! What a gyp.
However, when I got out of the first tutorial and could pick a new power, I saw one that looked neat -- it sent you leaping towards the enemy for about 100 damage (compared to the normal 6 to 12 damage). Using that as an opener, I was able to get through the missions a lot more quickly... it basically killed the enemies in a single hit.
Then I noticed that it didn't say you had to be a certain distance from the enemy to use the charge attack -- you just had to be 'moving'. So, I started holding down the 'back up' key while spamming 'leap attack', and sure enough, bam! bam! bam! I could just spam the leap, doing massive damage over and over with no delay (literally less than a second for the animation), until I ran out of energy. Which was NEVER because the leap attack had a very low energy cost (1 point, compared to 12 points for the useless damage-resistance debuff attack) since it was meant to be used as a one-time opener and then, if you were already in combat and 'not moving', an emergency escape.
...so I did that a lot, killing bosses and lieutenants and huge swarms of minions and a couple archvillains (Ferd and Gigaton). I'm not sure the attack is actually overpowered except for the lack of energy cost, but the lack of energy cost makes it really insane since you don't have to waste time recharging energy. There's a higher level claw attack that does about the same damage (in twice the time), but it costs 40. So I'd be able to use it once or twice, not sixteen times in a row. 9.9
Oh well, I mean, the game's still in beta. A few smoke-grenade level balance issues are expected.