I made the proposal in response to exactly the same instinct that Jim is reflecting here. If people really need a prefix syntax for decorators it would be best to at least _start_ with an implementation that doesn't involve core language changes, because the whole area looks quite perilous from a language design point of view.
We *had* an implementation without core language changes, but it was a postfix syntax. A prefix syntax should be designed with future usability in mind exclusively, unconstrained by "implementability without language changes". That's a much more stifling requirement than the requirement that existing code shouldn't be broken (which is stifling enough in itself but IMO unavoidable). --Guido van Rossum (home page: http://www.python.org/~guido/)