Is 'bloody fantastic' the reponse you want?! :D
I replaced a G12H30 (I am not a fan of this particular speaker) with one in my Bogner 1x12 cab and now that it has broken in it has made a world of difference. The best way of describing it's effect in tone, especially clean, is that it adds an almost three dimensional quality to single line notes of chords and is extremely responsive to picking dynamics.
With drive, it allows the character of the amp to shine through and retains clarity, even under extreme gain. It's become my favourite speaker and I am considering replacing the Vintage 30's in my Bogner 2x12 cab with them.
I use a Bogner Duende or Ecstasy 101B with the cabs and whilst it works equally well with either amp, the observations above were noted with the Ecstasy.