Yup, they are so bent on lying to you about the storage on RT that they even setup a page to explain it all to customers - http://www.microsoft.com/Surface/en-US/storage.

Additionally in the basic specs, you can see a #3 pointing to a note at the bottom that tells you that - "System software uses significant storage space; your storage capacity will be less. See surface.com/storage. 1 GB = 1 billion bytes. "

Yes, absolutely they are being dishonest and sneaky here.

Let's also not forget about how Apple does the same - "2.1GB = 1 billion bytes; actual formatted capacity less.", except I don't see a page that explains exactly how much is available, like Microsoft does.