The main benefit is no advertisements. If you pay for it, I'll give you an @dreamincode.net email address. You get increased upload and PM storage.
The best part is pages load faster because there are no ads, and you are supporting dream.in.code.
Cost is $2/month or $15/year.
You can get a free DIC++ subscription if you have an established web site and add a link to DIC some place. Or if you contribute 500 kudos worth of tutorials/snippets. Or if you become a DIC Greeter by welcoming people in our introduce yourself forum.