I worry about people reporting that Cloudflare and removing it or using it did x to rankings. There are a ton of variables to take into consideration. How do you have Cloudflare configured? Have you enable something like compression which is already being done on your site. This will slow you down since you basically trying to compress a file that is already compressed. The list goes on and on. CF is great for the reasons many have posted but some of the Cloudflare features can be done better with other programs and use Cloudflare for what it is best at. How do you figure out if it is hurting you? TEST TEST TEST. Google has continued its push toward speed and turns up the algorithm every month. It used to be Time to First Byte (TTFB) was all that mattered for rank position. Unfortunately, that is no longer true. The debate here is accurate and most likely every post is correct but I doubt it's CF is the issue. My rule of thumb is to always assume I screwed up something during setup since most of the time there is an issue like this it's a checkbox, a slash, or something stupid I missed. Google wants what it wants so all but a few of my client sites have pagespeeds in the 90's and rank on the first page of results for keywords they "should" care about.
As most of you know there is still a ton of other stuff that can ruin your SEO but after running CF through a buttload of tests with the members of an SEO testing group I belong to. Isolating using or not using Cloudflare has resulted in a positive statistical difference while using CF (if configured correctly).
FYI, we saw the same advantage using other CDN's too. Is one CDN better than another? Need more testing for that but so far the difference between them has no clear winner when using the same configuration or as close to the same that we could get.
Been with this testing group for a few years and I trust our results since the testing procedure debates that happen either put me to sleep or give me a headache and following the results have either helped or had no effect on my client sites. Normally it's easy to tell why some clients had no effect and normally shines a spotlight on a different issue.