What I like most about OCaml is the strong community around it. There are other things that I like a lot: the beauty of mixing types, pattern matching, functions, and lexical scoping; the higher order functions that seem a very natural and simple way to abstraction; and others. Without these I would not spend so much time with OCaml. But if I have to pick just one thing I like, then it's the users. Whenever you have a question you can be _sure_ that you will get an adequate answer within a day. In fact I have seen discussions on mailing lists happening practically in realtime.
What I hate most about OCaml is the arrogance of some of its users. The "our way is The Way" attitude. It seems that mentioning C++ in a positive way is sure to attract attacks. Curiously, I have never seen such a reaction from one of the developers of OCaml (Leroy, Dolinguez, Garrigue, etc.) It is perhaps an instance of the group attitude I hate so much: people acting irrationally just to get a feeling of "belonging".
As strange as it may sound I like rainy whether. I like to smell the earth when it rains. I like to stay in house and study when it rains. I like to walk thru rain (without an umbrella). I like to swim in the sea while it is raining. I like it.
But large quantities of rain can cause trouble. I've recently found out that my grandmother's house is in danger of collapsing because of the large quantities of water that imbued the earth.