Whether or not it's worth it is completely up to you. Home Premium has two features that Home Basic does not: Aero desktop and Media Center. If neither of those features appeals to you... then stick with Home Basic.
Aero does offload the rendering of the desktop from the CPU and uses the GPU. Even so, it doesn't seem to make a huge difference in performance either way. It does look a lot nicer, but you have to decide if it's worth the extra $20.