Apple is generally consistent with their User Interface (UI) design and mostly follow their Human Interface Guidelines but one application where they continually seem to ignore this and totally throw consistency out the window is iTunes. And no more so than in the latest version: iTunes 10.

Each major version shows off new features and more often than not, UI changes. I'd wager that Apple may be using this as a springboard to test future User Interface concepts on millions of users, as they did with the dreaded Safari 4 Beta. Once in a while, some of iTunes best ideas appear within OS X, for instance the refined, minimalistic sidebar in Finder or in Mail.

The 3 Tapbots apps: Weightbot, Convertbot and Pastebot are 3 of the best, most
unique, elegantly designed interfaces on the iPhone. They are also exceptional, highly functional apps and I sometimes play with Convertbot just for it's interface.

A highly recommended read at Cult of Mac