I'd never seen Rain acting before, actually, I'd never seen him at all, period. The story was really good, it had no flaws to my opinion, it kept my interest at its highest to the very end. I enjoyed the presence of Bo Na, the little girl, so witty dialogues with her father (we have a saying in Greek, 'you may find the truth either from a crazy man or a child', which was just the case), that was the highlight of the story.
Overall, the acting of all actors and actresses was superb -I read a review for the bad guys that was a complimentary one and I agree, hate/love reaction of the viewer.
I liked the parallel universe story, it was not over the top.
My recommendation is a must see one. Welcome 2 life was one of the best series I've watched so far.