An enabler for manipulating -1/-1 & +1/+1 counters in sets where they and charge counters matter. Would work well with say (((Heedless Ogre)))

I like the idea, but the execution could be stream-lined with minimal loss of use:

", Remove a counter from target creature you control: Put a charge counter on target artifact you control."

Normally, only creatures get +1/+1 and -1/-1 counters, and only artifacts get charge counters.

But at that point, it's basically a slightly more restricted Power Conduit. I mean, so is this, really; about the only thing this can do that Power Conduit can't is charge up your Mirrodin's Core, in case anyone cares.

­Darksteel Reactor and a Persist creature, the persist creature comes back, you shift its counter to the reactor, when the creature dies it has no counter so persist bounces it back again...rinse & repeat. EXAMPLE ONLY

Yes it is a niche card, but Magic has always had a place for niche cards that can go into somebody's crazy combotastic deck.

I limited it to -1/-1 & +1/+1 > Charge counters to keep the cost down and to play into the name - it either absorbs pain (-1/-1 counter) or Inflicts pain (+1/+1 counter) and converts it to a charge for...whatever.
I could have it cost 4 and make the counters go both ways by adding a 2nd tap ability that removes charge counters.....etc but that wasn't what I wanted.

Isn't that all stuff that's possible with Power Conduit though?

Yes it is but I only wanted the shift going the one way. This is one of the cards where I came up with a name and then had to fit the ability to it. Is it strictly worse than Power Conduit? Definately. Does it have uses that power conduit doesn't ? yes (not many - as Alex pointed out, you can use this to add counters to your Mirrodin's Core.
Does all of that mean this shouldn't exist? I don't think so. Given the limitations of this compared to Power Conduit, it could possibly cost