It was really very good indeed, and rewarded with plenty of well-deserved applause. My only niggle was that, perhaps because the stage was mostly occupied by the orchestra and chorus, the soloists sang, rather than performed, their parts; since the plot summary in the programme was fairly sketchy, the lack of action meant that it wasn't always clear what was happening in the drama at any particular time or where (the set being definitely minimal - translucent painted and lit drapes) it was taking place.
Good enough, in fact, that I felt it was a real pity that there was to be only one performance - I'd certainly have wanted to see it at least once more. Waiting for the Barbarians just may displace Akhnaten as my favourite Glass opera so far. There is a two-CD recording of the 2006 Amsterdam performance available if you want to give it a listen; Amazon has details here.
Many thanks to mister_jack for the transport to and from, to mrph for being the ticketmeister, and to both of them and jambon_gris for an evening's good company.
And now I'm really weary, so off to bed...