I always thought this was a great idea. Not that the torrent app in opera is anything to write home about, but it will get the average user a much smoother experience. No need to install and use another program Azureus(sp?) and learn how to use it. Just click and download.
(I'm not bashing opera or it's torrent application, but it certainly doesn't have the array of features a BitTorrent only client has(Superseeding, Queuing, etc.).)
Unfortunately the popularity of opera is a downfall, this is a great idea. It would be nice to have a torrent application in Firefox, or even a plug-in that asks to auto install when you download a .torrent file.