After having quite a few hammies since I put my last post on here about not liking it apart from a temp/hospital cage, I definitely have changed my opinion on them a fair bit.
I'd not keep a Syrian in one unless very elderly and frail, Duna's have given 2 of my past elderly Syrians a new lease of life and a couple of extra months that I don't think they'd have had in bigger cages.
I also now think they're not too bad for a Single dwarf/chinese. Chinese hammies can often become stressed in large spaces (not true for all obviously) as they are very shy by nature. I had to downsize my previous Chinese hammie to a Duna from a ZooZone as she become stressed with space as she aged. I think it does vary from ham to ham but I definitely think that they're a lot nicer for a single dwarf hammie than a lot of cages out there