Yeah, even though GoG was designed and is usually (or always? is there a counter-example?) implemented with the OOP paradigm, I've always found that its principles were better abstracted with functions and combinators. It's a product of its time.
I believe the original GoG theory/specification does not suffer from the same impoverishment and flaws, it having been formally proven and all... But the same cannot be said of any particular implementation "merely inspired by it". I would very much like to implement it in a pure FP language like haskell (and/or perhaps even proven correct with Coq) some day, that would be fun.
Myself, I think ggplot2 is one of the more solid and least-crippled implementations. Unfortunately, my distaste for the R language is such that I hope I never have to use it again.
