IMO the LL is only worth it on All-Stars, since you have the ability to save. It's a fantastic game though -- it may just be an SMB "expansion pack", but it includes more levels than the original SMB (worlds 9 and A-D), and the challenge is supremely difficult. Plus, you get to play as Luigi with meaningfully different abilities from Mario.
They ought to just release All-Stars for the SNES and charge 1200 points for it. Hours and hours of classic Mario goodness.