There appear to be three ways to do deep links on the iTMS without rolling your own URLs: one is to drag any hyperlink (not individual music tracks, but underlined artist or album names) to an application that supports drag and drop. You can also right click on a hyperlink or an individual track and choose the Copy Music Store URL option. That’t how I constructed the links last night. Doing either one results in a hyperlink using HTTP that goes to phobos.apple.com.
I’m less enthralled with this for a number of reasons. Number one, it requires embedding the script detector in the head of each page that bears the links—not a big deal when all pages on your blog are generated dynamically, but still something of a hassle. Number two, the iTunes Detector may be a lightweight piece of code, but it is not a lightweight user experience. I think I would rather have a link fail than pop an installer dialog over my blog pages.
That said, I’m not sure the direct link methods are any better of a user experience. The page on phobos.apple.com that is opened by these methods calls iTunes and then sends the user back to the calling page on Internet Explorer for Windows; on Safari, it appears to automatically close the calling page or tab. (Verification welcomed; I’ve only tested on my own machine.)
(Updates: See the comment from Greg about pulling a direct link from the deep link tool, and see the expanded version of this post with context at Blogcritics.)