Peppermint OS is a Lubuntu based, GNU/Linux distribution that tries to integrate cloud based applications with a desktop operating system. As a model for this, Peppermint OS ships a few cloud based applications like Dropbox, Pixlr express and image editor, Gmail..etc.
Instead of providing a completely different experience, Peppermint tries to deliver a familiar environment with cloud application integration. That is how it is different from other operating systems trying to deliver cloud experience, including Ubuntu Netbook Remix, Google Chrome OS, and Moblin ..etc.
The core desktop environment used in Peppermint OS is LXDE, which has been proven as a lightweight, mature desktop environment for years. Instead of shipping all components in LXDE world, Peppermint OS uses a customized set of applications to provide better user experience. As a part of this philosophy, it ships applications like nemo file manager, Chromium browser, mintinstall software manager ..etc.