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You did not get 33GB back. Snow Leopard measures space differently. The larger your hard drive, the more space it looks like you get back.
I have a feeling that them moving to base 10 is going to cause a lot of problems for people.
Here is the support document on Apple's website that talks about how Snow Leopard measures drive capacity differently than Leopard and below: http://support.apple.com/kb/TS2419