Lens: Canon EF 70-200mm F4L IS USM and Canon EF 100-400mm F4.5-5.6L IS USM

I rented both this lenses today for the weekend. I am hoping to go to the PC Show 2011 and Formula Drift event on Sunday. Both are considered telephoto zoom lenses which are what I am lacking after selling off my EF-S 18-200mm.