It also has better wheels, by most people's standards. And Rival over Tiagra is a pretty significant improvement that is easier to quantify than the difference in frames. Don't be fooled when that Felt says 105/Tiagra equiped...the only 105 piece is the front derailleur. I would rather get an aluminum bike with full 105/ultegra than a carbon one with Tiagra at that $1800 price point.

From a purely aesthetic standpoint, I don't like the look of the lugged carbon construction on the FC100, but not sure if that really translates to performance. Makes it a bit heavier though. testrider.com recently did a review of the FC100, so you might want to check it out. I think it was fairly positive.