http://itunes.apple.com/WebObjects/MZStore.woa/wa/viewSoftware?id=320654497&mt=8 First impressions, it seems very cool. You can have up to 200MB local storage, meaning once you've downloaded a file, it appears in "Recents" and is available without having to re-download. It states in Settings/Local Storage that "Audio and video files are streamed and not stored locally". Browsing seems much quicker than alternative iDisk apps I've tried, QuickOffice/MobileFiles, OneDisk, ReaddleDocs etc. No advanced PDF features though unfortunately, i.e. no bookmarking, fast-scrolling or go-to-page functionality. There's also a button next to each file to quickly share it, by opening an email with a link in it, and options for expiration date and password.
The handling of the public folder seems to be the only real advantage over the already existing apps. But QuickOffice can edit the documents and ReaddleDocs can copy files from the web or the camera roll to the iDisk. So as long as you don't need to change your public folder password from the iPhone, the "alternative" iDisk apps are the better choices.
Great software coz its free, however I'll still use ReaddleDocs as the most advanced solution for this case. (i think it's needless to say difference between them). But sure, for people who don't need bookmarks, emails, file management, MobileMe iDisk is perfect and simple solution.