1. Free to get started, only start paying when you're generating enough traffic. (500MB storage and 5 million monthly views)
2. Very simple to use.
3. Really simple, powerfull API's (data, images, mail, users etc.).
4. Python's a great language to work with.
5. Leverage Django, Pylons, Google's WebApp or whatever you need.
6. Scalability isn't an issue, your site will scale as it needs to.
7. Easy to model data - no need to setup and maintain a DB, indexes etc. You use a Bigtable implementation with auto-indexes (can add own indexes also)
Alot of C-based modules are disabled, however there are often pure Python implementations of them. Check out the documentation. It's very easy to follow and you'll be up and running in no time.