Oh, don't get me wrong, I'm a big Narnia fan. I just felt that the Christian allegory, which I had been fine with throughout the other six books, suddenly got pushed to the forefront in TLB; I felt it was a book that wanted to say "Look! Judgement Day is coming!" rather than "I'm going to tell a good story while being inspired by my faith to imply things about it." I found the story very depressing and then the happy ending didn't ring true with me - they'd been through so much, people had died, it really got to me (I was ten, okay) and then I just couldn't believe in the ending. Not to mention I think it's a bit rough that they all died so young. At least Digory and Polly had had good long lives, but Jill and Eustace were only sixteen, which seems kind of harsh to me.
Ahem. Now I'm going to do the rant you actually asked for...