The plugin is turning out pretty sexy if I say so myself.

Karma can be turned on/off per forum. If it is on, next to every post you'll see:

Karma: 1 [+] [-]

The number is the current post karma and by clicking + or - you can increase/decrease the level.

The administrator can set an option in the admin panel so that the karma increments/decrements only after x number of votes, so say admin sets that option to 20, that means 20 people would need to vote for a post before the karma would increase/decrease.

It will track which posts you've already voted for and show:

Karma: 1 Voted

....if you've alread voted for it.

Forums not supporting karma will show:

Bad Karma

...that lot is template based so easy to change.