I guess that depends on your perception. I've never known a UK soap to portray DID before, they probably have on one that I don't watch, maybe Hollyoaks? But I doubt they'd be able to do it justice in the same way because Days at 38 mins per ep 5 days a week has really been able to explore the Abby storyline in such a deep sense. I think it's been fascinating, it's one of the best soap stories I've ever seen. I totally get why people would find it annoying if they've seen it all before though.
I like the way the American soaps don't court a load of controversy for such controversial stories like this. The UK soaps would get stick.
I feel like the US soaps explore storylines and characters better because they have more air-time. That can be a negative too though, some stories and scenes feel dragged out and things don't move quickly sometimes. Days offers a very different experience to the other soaps I watch IMO.
I think you have to hand it to the actors too. They're given such ridiculous and difficult material to act out but the girl who plays Abby has been awesome.