Why? What are the benefits you're getting from it?

Imagine this: I have 3 dedicated servers, on one I run the web server and on the other the mysql database and on the third one I have another mysql database.

Do I benefit from using the master/slave setup?

Well, once i has three dedicated servers running my forum I will post back here and let you know. ;)

Nope, not yet :) We'll get there, though.