Very happy with this wheel upgrade. I thought about purchasing carbon wheels for a while. I looked at several brands at different price points/weights etc. Really glad I chose Zipp 303. The price from Merlin with Continental GP4000s II included was also very good so that helped:)
I got the 808's, they much faster than my training wheels and have been stable in some pretty strong crosswinds. I seem to be able to hold a good 1.5 - 2km/h faster on my normal rides.
These wheels seem slightly heavier than my Bontrager RXL but they more than make up for that with their aerodynamics. Awesome! I had 7 new PR's after my first serious ride. One thing to note: when I first installed and took them out for a ride, I noticed a clicking noise. It turns out that the stem extenders hit against the carbon frame on every rotation. I solved by getting a heat shrink tube that fit snugly over the valve stem extension and inside the hole. Problem solved! Wheels are fast, smooth and silent! Definitely recommend.