I have not, but from screenshots it seems only a minor reskin.

There was a Linux client I saw a while ago—Spring Mail or something like that?—which first downloaded your email from your provider onto their own servers, then your local client got them from their server. This additional cloud step is what I want to avoid.

Yeah, having the option is not a bad thing. Nothing changes for those who use the apps or want them there, but it lets people remove them if that’s what they want.