WP-Cache is lauded as an excellent plugin, but it suffers from updating content frequently enough for developers to be able to change their site data regularly, especially in terms of tweaks, widgets, or CSS edits.
Among SEOs, there are only “smarter” clients who already know what to do about SEO. I come from a background in web development where the developers have no idea what SEO is and why it’s important. There’s a whole world out there that’s just like these people. We can still market to them and grow smarter.