The 06 models are a bit cheaper than the 07-10, probably because they were a bit cheaper when new. The biggest difference is the frame materials and I'm wondering how much of a difference and premium that's worth. There are also some geometry differences and I'm wondering how differently the two frames will handle, since I can't ride either before purchase. The components are almost completely identical between the two. I have an 07 Sport now which is neither here nor there in terms of geometry and material. The 06 I'm looking at is a good $300 cheaper.
06: A1 tubing, carbon fork with aluminum steerer.
07-10: E5 tubing, all carbon fork, carbon rear stays.
Geometry differences (other measurements are same),
06 vs 07-10
Wheelbase: 1037mm vs 1032mm
Trail: 61mm vs 64mm (head-tube angle 72.5 vs 72)
Chain-stay length: 450mm vs 440mm
Front-Center: 597mm vs 601mm
The longer chain-stays and wheelbase on the 06 indicate to me a slightly more stable ride, but the lower trail ad front-center indicate the opposite.