Check should warn users who are not using Torbutton.
Sorry nick, didn't know who else to give this too and our "vendibles" pages are not easy to find.
Anyway, we have waaay too many users showing up in #tor and using a dumb browser, and studies indicate that 20% of our users use Torbutton (see bug #1801 (closed)).
Many of them test their browsers on check.torproject.org. We should provide a link to the TorButton and Tor Warning pages if check.torproject.org does not detect a Torbutton user agent.
I can provide tests we can use to detect this generally while Tor is enabled.