I've only really travelled to one place (short holidays aside), which is India, which was very different to my expectations.
Having thoroughly looked through my guidebook, I was expecting the worst: I thought there to be mosquitos everywhere, unbearable heat, etc. In fact, I did get bitten a lot, but rarely did I see mosquitoes flying around (and I first thought that my vision would be impaired by them!). The weather, whilst admittedly being hot, was bearable with my type of stay (working throughout the day's heat in a cool office). I suppose I expected it to be vastly, vastly different from England and in the end, it turned out to be much more pleasant than I had thought. Wouldn't it be nice if all of our trips exceeded our expectations?!