I think the slight unbalance in the karma "formulas" do not make a big difference. There is usually visible diff in the first 2-4 weeks and probably after 1+ year, but the first period passes quickly and the on the long run it does not matter.

With this being said, Yes to karma and some points to consider:
* Community contribution (thanks/bugz/brains), development is good to be rewarded as before
* Learning should be rewarded too, so new users can gain karma (this promotes the right behaviour)
* If there would be an action handling system in the background, that could make it easier to track/give karma on community actions

Hopefully I can make all of this into a compelling proposal on the weekend