I was reading an old email from devCentral and found a link that was supposed to described how to detect enhanced devices. It seemed quite interesting.
The passage (seemed more like an FAQ) was pretty disappointing.
I think that parsing the accept headers is not enough, unless you think that a device that supports XHTML is an enhanced device. To me, an enhanced device is a device that supports images, colors and has a big screen. A stylus is a big plus, of course.
WURFL is certainly a much better starting point than simply HTTP headers.