Bummer, looks like Edit in TextMate… is not working properly from Mail.app (or likely any WebView) since the Safari 3.1 install. The content of the WebView is not transferred to TextMate. The MacVim folks actually mailed me about it since they're using a modified version of Edit in TextMate… with MacVim. Anyway, I won't be able to look into the matter for a couple weeks in-case someone else wants to take a crack and send Allan a patch.
j.