Paul Miller wrote a very interesting and inspiring editorial on the shortcoming of todays operating systems. It's a great read, and Mailplane seems to help solve these OS problems:
I'm gonna go a little crazy here and say that we're not necessarily going to leave the desktop behind and dive into some glorious world of just needing a web browser. In fact, when I think about some of my favorite applications, they're the exact reversal of that trend. Mailplane puts my Gmail in a familiar, functional desktop context, Tweetie makes managing Twitter a casual, persistent activity instead of a chore, and iPhoto manages my social photo sharing folders for me so I don't have to stare at endless web forms and upload dialogues to get stuff on Flickr.