As a rule, NEVER EVER use CNAME's within AWS on Route53. You should always use their A Alias function. This provides near instant changes when you need to adjust a record. This only works on aws resources, but it is a great feature they built in.
I know, I know, I hate it too. We're working on it. Just wanted to share the workaround.
[1] http://wiki.nginx.org/CommandLine#Loading_a_New_Configuratio...
[2] http://www.mgoff.in/2010/04/18/haproxy-reloading-your-config...