What do you think of Quagga compared to XORP as a dynamic software routing engine? What are the technical merits of each engine comparatively? Additionally, what do most people think of them from a programming view. Who has manipulated networks using these enginers? I was wondering from an OSPF, routing, BGP protocol user's perpspective.
The following does not answer your question completely, but the Vyatta open source routers and the OpenSolaris customer gateway software for Amazon VPC both use quagga to implement BGP support.
From the wikipedia entry for XORP,
"The software suite was selected commercially as the routing platform for the Vyatta line of products in its early releases, but later has been replaced with quagga.