Trek and fisher are made by the same company. Basically trek owns fisher. I own a fisher and I love the way it rides. I was lookin at cannondale when I was in the market for a bike and I like the geometry of the Fisher better. Cannondale was going through problems at the time because of the demise of their ATV/ Motorcycle division. Cannondales are generally lighter bikes. I'm not sure if you are Pro american made or not but Cannondale is made in bedford, PA. Higher level trek and fishers are also made in the States.
As far as seats go I love the specialized body geometry seats and regardless of what seat I buy it has to have a love channel.
poison ivy sucks I have some right now that pretty much covers my legs from the top of the knee down. There have been several times I've had it over 99.9% of my body. I would take a hard fall on my bike over poison ivy but what really sucks is when your hard fall on a bike lands you in poison ivy.