Super Meat Boy
I was pretty disappointed at how poorly Super Meat Boy ran on my netbook (in the default settings -- launching the game with -lowdetail runs great). But I can forgive the two-person team for having some polish issues. When the game is playable, it's very playable, and presents not just an intense challenge but also an interesting assortment of puzzling platform levels.
While many of Super Meat Boy's unlockables and special levels may remain impossible to me, it's comforting to know that I can, in theory, "beat" the game much more feasibly. But the special characters, especially Mr. Minecraft, taunt me endlessly.
Progress: Hell!