Hi Jed,
I too had this question regarding outbound gateway selection behaviour in Lync - will Lync use the first GW specified in a route definition until/unless that GW is unavailable, or will calls be routed in a round-robin/load balancing fashion across all available GWs in the list?
This Blog suggests that the answer is the latter - that calls are load balanced across all available gateways in the list:
http://blogs.pointbridge.com/Blogs/Crockett_keenan/Pages/Post.aspx?_ID=12
I just wondered if this is in keeping with what you have observed in production?
Thanks,
Garry