No speaker is perfect, but if you love the Greenback sound, you ought to give this a try. Classic rock crunch tones sound colorful and detailed.
Side by side, they're slightly less bright than current production Greenbacks, but they don't sound dark or muffled - nothing on the level of a Creamback and the EQ of the speaker seems to help accentuate the tone of the note in the upper mid-range and reduce the "fizz" you can get with some M magnet speakers.
I can't claim to have tried it with every amp in the world with it, but with my Marshalls, I'm impressed.