After years of riding Harleys I found the tiny diameter grips on my F6B to be very uncomfortable. Someone suggested grip puppies. WOW. Just did my first ride with them today and they make a great difference. Much more comfortable, although they are very expensive at <$10. Easy to install and they feel great.

So far the two cheapest things you can add (grip puppies and hand wings) have proven to be the best extras for the bike.