Yeah, developing for the mobile web got a little bit harder with the new generation of mobile browsers that will render media="screen" even if there's a media="handheld" stylesheet. That's something iPhone and Webkit for Nokias made worse. At least you can use media queries but still...

If you're really interested in the dos and don'ts and also the why's of the mobile web, I strongly recommend Cameron Moll's book. Chris links to it in the article. 

Oh as for Opera Mini, it's worked like that ever since the first release. Pretty handy if you're accessing over the GPRS. I still think it uses the proxy regardless if you're accessing via Wi-fi, which sometimes can be a bit annoying.