One of them would probably be the ability to "visit" my imagination. Think of it as a form of lucid dreaming, or maybe a holodeck... except that for the time I am there, it would be "real". Or as real as I want it to be, anyway. I have a very vivid imagination, and one of my greatest regrets is never being able to truly see or experience any of it.
Just think about it - you have a book in your hands, The Lord of the Rings maybe, and while you are reading you are actually, physically there. You speak with the characters, fight evil with them and see the world not like a movie paints it, but rather what you thought it was from the description in the book. How awesome would that be?
Obviously it should be a time limited power or I'd never return to the "real world" again