I use and love this extension. The main complication that would prevent it from being a mainstream solution to cookie clearing is automating the decision of when to create a new container vs continue to use the existing one when links are clicked. Going by domain name (using Public Suffix List) breaks a lot of SSO implementations, and the occasional payment processor/verification flow, and other situations that redirect to another site, but pass information (or save state to have on return) via cookies.