Well looks like Firaxis thought their Special Ability weak as well so they have tweaked it. In the version I played it gave you the following bonus: Forests and Jungle are treated like roads when they are within your territory. This means they give a bonus to movement and also help with setting up your trade network.
This sounded improved on paper, in the game though I was always expecting my units to move faster through forest while I was exploring. Of course this wasn't the case as very little forest was in my initial city radius. It was really neat to only have to build a few roads to get a trade route between my first cities though. You can accidentally destroy this though, since I build a plantation on a forest tile, which essentially destroyed my trade link. Bummer.
Othe than that I see a problem with the smaller culture area you have in Civ V as compared to Civ IV, which makes the Iroquis Special Ability not as good as it looks on paper, in my oppinion.