I've entered 12 pages worth of recipes into MFP. If I want to log something I haven't had in a while it takes forever to scroll through all those pages and find it. It would be awesome to have a way to search within my recipes.
Also, being able to share recipe books with friends would be fantastic! My husband wants to start using MFP but doesn't have the patience to enter all of my recipes. I could see (1) sharing my whole recipe book or (2) being able to share meals with friends sort of like how you can copy whole meals from one day to another within your own diary, but being able to copy a meal to a friend.