I saw this yesterday and had really been looking forward to it, but didn't enjoy it as much as I hoped. I can't fault the acting or production; rather, it was the play itself, I think, which whilst typical of Shaw in the respects listed by @neilvhughes above, isn't one of his best. Only to be expected, really, or it would be revived more often but I was glad of the chance to see at last a play by Shaw new to me, and all the more so at the Orange Tree, which is still one of my favourite venues even if the programming is no longer much to my taste.
I saw this last night with my students, and we thought it was extraordinary. A really fine production, well-acted across the board, beautifully timed and paced. In my view, it's one of Shaw's plays that holds up best--wonderfully entertaining, and still politically relevant (read Elinor Cook's essay in the programme). So glad to have the chance to see it.