To me being in the present moment is like lifting a cloud hanging infront of reality, your memory's and projections of the future are the cloud. The only thing you are sure about is the present, so to discover how reality works you have to explore the now. Because the mind has a tendency to pull up smoke quickly in the form of illusions (past/future/boredom) its a very difficult practice to stay in the now. I'm only at the start of that journey, but I can see the benefits at the end and frankly I'm scared shitless. Its scary to explore reality, but fear is just another way of your mind to distract you so thats what I'm working on now.
Anyway so for me being in the now has the benefit to see things as they are and accepting them without forming mental images.
Ps This is mostly from
Mindfulness In Plain English which is a great e-book, and I suggest anybody reading it who's interested in meditation/being in the present. The writer has a very engaging and elegant writing style once you get past the first few pages...