I think it's still too early to tell, but I'm impressed with what we've seen so far. I also like that they have really taken their time with this story and allowed Kathy to settle back in slowly. Nevertheless, we will have to see how Ben and Ian react, and see how Kathy fits back into the Square, before we can make a proper judgment.
To be fair to the writers the biggest hurdle they had to get over was actually bringing Kathy 'back to life' and on that I think they have succeeded. There's been no public outcry; most viewers seem to have just gone with it. As much as I hated the decision to kill her off in the first place, I was always firmly of the opinion that dead characters should stay dead so for years I was adamant she would never return. Obviously I was proven wrong on this

but I've said all along that the explanation for her death will have to be credible for it to be a success. Everything hinges on that. The Kathy we knew would never have willingly abandoned her children, so the only plausible outcome would be one where Kathy had to go into hiding for their own protection. Judging by what Kathy said to Sharon tonight it seems that was the case, which is a huge relief.
Killing Kathy off was one of the biggest injustices in the history of soap, so if DTC can pull this story off then the man will have massively gone up in my estimations. I think it's testament to his sheer love for the show that he has gone to such lengths to restore an original and important character. Also, Gillian Taylforth is a legend and it's genuinely brilliantly having her back.