You'd be a fool not to download these free Guitar Hero DLC songs right away.
Why? Because they're free with no catch, and it adds to your song setlist choices when you play with others online. All you need is some free space on your hard drive (Xbox 360) or SD Card (Nintendo Wii).
It's always dumbfounding to see a player with zero DLC. Why wouldn't you at least download the free ones? One can only guess they simply aren't aware of the Music Store's free DLC.