Well, besides just liking the rain?
1) I like the way things look when it is raining; I think it is pretty. Raining at night when all the lights are on is even better - especially at MK where it looks like they are sparkling. Watching the rain on the water from a hotel balcony is relaxing. Watching a big lightning storm is always cool. I used to live in Florida and miss the big thunderstorms.
2) There are less "spacers"; as my husband and I call them. Spacers are groups of people that walk really s l o w and space themselves out just enough to block a whole walkway so you can not get around them. When it rains the spacers are ducking into doorways and under trees, so that means nice wide open walkways to walk on.
3) We always seem to have a bit more fun when it rains. It is like all worries just wash away with the rain; we can all act like dorks and not care if we get wet, what our hair looks like, etc. I think I have more pictures of our family smiling and laughing, wearing our ponchos and looking like a pack of drowned rats. WDW is one of the few places where your butt can literally be soaking wet and there you are still grinning like a fool!