I was really drawn into Winter's End at first, as the set-up of the orphanage/school was interesting as were the dog-men. It continues at a decent pace with escalating excitement as the reader discovers more and more about the world; though the love story part was less believable, with two sets of teens falling in love at first sight.
For me the book really started to fall apart when everyone from the government seemed to be incompetent and easily defeated, and that all the power the government became unbelievable. The final rebellion worked out way too neatly, and the whole book wrapped up quickly in a very neat little package. If I had read this before Hunger Games, it might have worked for me, but with a weaker evil government, a way too tidy ending, and far less perilous peril, it just disappointed me in the end. It also didn't help that while it starts out being about the two girls, the boys take the lead and have all the fighting power and leadership skills, and the girls end up singing, cooking, and longing for their boys. Katniss (and Katsa from Graceling) have raised my expectations quite high for girls/women fighting evil governments.
I think that if Winter's End had been expanded into a second book, letting things play out more fully and giving the girls more of a role in the rebellion (which you really think they are going to have for a while) I would be able to recommend the book more. I'd give it 3 out 5, because it started out really well and kept me reading and wanting to see what would happen, it just didn't finish strongly. I'd give it to teens who like dystopian books, and those who are ask me for something to read while waiting for Mockingjay, but only after I had recommended Graceling and Maze Runner.