After 2 and a half grueling hours, I've beaten VVVVVV. 
 
Forget Demon's Souls or Shin Megami Tensei: Nocturne. VVVVVV is the hardest game I've ever played. Oof. There are a few things that bothered me, like some weird checkpointing and slippery controls, but VVVVVV is so charming and funny and retro and a pleasure to listen to. Money well spent, no doubt about it.