Since im here im going to respond to this with a couple of things.
"While Cloudflare offers many optimization services and DDoS protection, many of them break Magento and Wordpress functionality."
I've not had any issue with this. Typically if something does break in WP or Magneto its pretty simple to fix. Personally, i dont run WP sites without cloudflare, its too much of a security issue.
" Implementing caching and Google PageSpeed with Nginx or Apache shows much better performance,"
You should do this anyway....
" Worse though, Cloudflare doesn't allow you to use your own SSL on any plan under $200/moth"
Sure it does, i run 40 + sites on standard Comodo SSL certs on Cloudflare pro without issue.
"If you're a Pagespeed/YSlow nut, they you'll really be upset to learn Cloudflare adds a security cookie to everything, so there is no way to have serve content on a cookie-free domain when using Cloudflare DNS"
Thats a fair point, though perhaps not such an issue in most situations.
"Customer service is also slow and mostly automated, so don't expect great service on unpaid plans."
Again i dont really find this. Most of my accounts are CF Pro but for those that arn't, i dont notice any difference in support level. I know Business and Enterprise plans get faster support but for $200 + a month, i'd expect that anyway.