freitasm - 7:27 pm on Jan 29, 2013 (gmt 0)
I use CloufFlare as a CDN (serving images, CSS only from a cdn.* subdomain). All the main content still comes from my main domain.
I did try Cloudflare in the main domain for a while though and because of our users' profile (location, etc) it didn't make sense continue using it. Also because I was seeing some errors that don't happen when served from our servers.
As a CDN, for $20 a month with SSL support it's a great deal. It does alleviate some load in our servers by reducing the number of images, css we serve directly.
Even when using Cloudflare in the main site (for a couple of months) I didn't notice any "invalid traffic" though.