This solves two problems: (1) the only visible/bookmarkable URLs are those without a #!; and (2) initial page loads can be fulfilled by a single request to the server. It doesn't solve the problem of URL discovery, but two out of three ain't bad.
Not sure what you mean by URL discovery. Although link/hrefs should be the same/legacy. What you could do is progressively enhance normal links. Javascript could disable the default behavior of a link <a href="/about/team" data-remote="true">About Team</a> and check and see if browser supports History.pushState. If it does it would just request the appropriate content for /about/team and update it client side, then update the url. If pushState is no supported, it could just request that link /about/team normally. This would be the ideal way to support both regular and progressively/JS enhanced pages (for speed).
