This blog entry describes how to upgrade from Ubuntu Breezy to Ubuntu Dapper Drake.
Read it here, it shouldn't be too difficult!
Ubuntu Dapper was originally pegged for release in April, but is now set for June. However, its already stable (in my experience), and markedly better than Breezy. Heres a brief guide to upgrading. This assumes youre already running [*]Ubuntu Breezy, like any sane computer user.