Winnie the Pooh is really odd. It was the first chapter book I tried reading to my son at 3 and a half years and I was shocked that he loved it. I was actually more shocked that I loved it. Of course I've known about Winnie the Pooh my entire life, but the movies, tv shows, watered down books, etc. really don't do it justice. The original A.A. Milne books, in my opinion, are hilarious in that the author's dry humor shines through. I thought some of it was so funny I would read passages to my husband after my son would fall asleep. Of course my son missed all that, which was why I was surprised he liked them too, but I think that he took them so literally and the plot lines were so simple, that he was able to enjoy them with minimal explanation. Now, 6 months later, he's less interested in them....we didn't quite make it through The House at Pooh Corner, but he hasn't asked to finish it.
Anyway, I'm not sure what type of child it takes to like Winnie the Pooh and what the best age for it is, but if you've never read it, I recommend at least borrowing it from the library. I suggest changing the tense of the first chapter (which is written TO Christopher Robin) so it's less confusing for the child, but after that, it's written in third person, which is much easier.