Carson, I'm in the exact same boat as you and it's served us really well. I'm using CloudFlare only to cache my static assets for a Node.js app and I've seen performance in Heroku (and NodeJitsu) go up as a result. I've also added some subdomains to CloudFlare so I'm sharding my static assets (cdn1.mysitecdn.com, cdn2.mysitecdn.com). Add in that all of the assets are Gzipped and SSL secured and I'm a very happy camper. My app on 3 dynos can handle 1000+ concurrent users/sec no problem.