User:BWolff (WMF)/CSP/8

Downsides

 * Old extension compatibility, especially pre-MediaWiki 1.17 extensions
 * Still in active development
 * Still todo fine grained control by extension (e.g. Recaptcha usecase)
 * Still todo, per user preferences for Wikipedia style mash-ups

CSP is a complex technology with many options. There are many other features of CSP I haven't covered here.