The more I think about the Iraquois and the 1upt, the better I think they are - IF they fight in forested areas. They can simply envelop the enemy units, and because of 1upt envelopment plays a bigger role.
If you play Civ 4 as Aztecs, and do a rush to Iron Working, and just start sending Jaguars into enemy territory with Woodsmen 2 on them, you'll start to get a feel for what I expect the Iroquois to be capable of.
You can literally shut them down to having one city for the duration of the game. It's super awesome.