The subject of the verb is "none." "of us" is a prepositional clause. It's tricky because "none" isn't singular or plural, but a good similar sentence is "Neither of us is perfect." You wouldn't use "are" here because you're referring to only one person. So I would probably go with "is" in this case as none is closer to being singular than plural
02/4/14 This is a gray area. Both sound correct to me. It depends on the dialect and/or the flow of the conversation as to which one would be used. Whether the use of ""are" instead of "is" bothers you depends on your pet peeves, the pet peeves of your teachers and parents and your acceptance of the use of colloquial rather than strictly formal English in this setting.
None of us are perfect is not natural, if it were, you would say "us are perfect.". Does that sound natural? The word "us" is not the subject! It may sound natural to you, but just because you have heard too many people use this horribly incorrect language. Please ask any English teacher.