It certainly isn't naturalistic but has been kitted out quite expensively and is certainly more attractive than Colchester's rather similar exhibit for this species.
For a chiefly rock and ground dwelling species like the Gelada, a couple of naturalistic Rock piles, a couple of concrete cave shelters and a small tree/some logs would have done just as well though. The male Geladas living in here will probably spend most of their time in one favoured spot anyway, huddled together asleep. I can't see them making much use of the rubber ropes etc, more suitable for Gibbons or other arboreal species. The floor may quickly become bare as soon as they pick out all the grass to eat.
I haven't seen Edinburgh's group but believe that most of their area is a large open field- the best location for a species which feeds almost exclusively by pulling up grass shoots. At Howletts the small Gelada unit (of 1.2+1) share an enormous enclosure with Colobus- the ground space available again being perfect for this species.
i agree that this isn't ment too be an immersive enclosure, however i see no harm with the wooden platforms as i think they will make nice use of them.