admin yes, but in order for it to work properly you need to push all traffic through it. For example, you couldn't just use it for DNS and expect the security side to work because it won't. In addition, Cloudflare can actually slow down sites rather then the reverse which is desired as it can significantly increase the TTFB (Time To First Byte - the amount of time it takes for the page to display any meaningful content). Cloudflare of course refute this and advise you to ignore TTFB but that's not wise advice when you start to add almost a second to the loading time of your site.
Your content can be fantastic, but if the site takes more than 3 seconds to load, or looks like it's doing nothing, people will simply click the back button.