I guess most MobileMe user have used other applications until now, such as MobileFiles for example. But kudos to Apple for taking this long time to get this up into AppStore.
“The new MobileMe iDisk app brings the convenience of iDisk to your iPhone and iPod touch. You can directly view files including iWork and Microsoft Office documents, PDFs, and QuickTime movies. And if you want to share a file with someone else, just tap the share icon next to the file to email a download link that works great with both small and large files. Watch this video to see how it works.” – via Apple.com