Regretfully, I have yet to be able to attend a convention of my own. But the feedback that I hear about them has always been positive. I mean, why shouldn't be positive? It's a win-win scenario for everyone.
Authors get the ability to brainstorm with other authors, figure out what has worked for them with regards to marketing their novels. Also, you get the chance to hang out with people who you only knew through the computer. Meeting the people who read your books is probably the biggest advantage because when you talk to them, they'll be honest about what they like and didn't like and you might just get an idea for a new book!
Readers get the ability to meet the person behind their favorite books and it makes them realize that we are not celebrities(although we would like to be!!), we're just as normal as the rest of the world. Plus, they might get some secret scoop about new books or some exclusive swag.
So if you get the chance to go to a Convention as either an author or as a reader......
GO FOR IT!!!