That's interesting, because I've heard that link syntax is one main reason people prefer Markdown to Textile. One issue with Textile-style links is that something like

  "Foo Bar":http://foo.com/bar.

is ambiguous, and the result depends on the parser. It could end up as

  <a href="http://foo.com/bar">Foo Bar</a>.

or it could end up as

  <a href="http://foo.com/bar.">Foo Bar</a>

The former is probably what you mean most of the time, but then there's no way to link to the (valid!) URL "http://foo.com/bar.".