So, any good? Definitely. But I couldn't shake the feeling that, fundamentally, it's a somewhat unnecessary affair that, while certainly entertaining for Monty Python fans (so we were happy), mostly serves to keep Monty Python alive for the "youth of today". That said, that's still a much better rationale for existence than many other shows have, so I shan't complain further. As it happens, and contrary to what I expected going in, the best parts of the show are actually the new bits that Idle et al. have added. These include a series of big musical numbers that very effectively pastiche and satirise the clichéd and overwrought songs of mainstream musicals (e.g. Act 2's "Whatever Happened To My Part?"). Largely sung by the semi-token female character, the Lady of the Lake, these were right on the money, and certainly the highlight of the show for me.
Overall: recommended. But don't go in expecting something to trump the film. That was excellently silly enough without extended musical numbers. And, I should add, the film has the benefit of the Bridge of Death scene.