Sorry to have been absent to the forums when you first asked about the Synapse, but since you went forward with the purchase, I can add my +1 to your purchase. I picked up a Synapse carbon frame on eBay in 2011 and built it out with a mostly Shimano Ultegra group. I love my Synapse! Yes, it has more relaxed geometry, but that works really well for me. I'm 5'2" and have the 48.

Congratulations, and be sure to share pictures!