Just finished the game after playing on and off for the last two months and methodically mapping everything over the last week, this is probably the best C64 game I've ever played. The difficulty curve was pretty much perfect (Every time I died I either got a bit further or learned a new trick). Encountered one tiny bug in world 5 (The scorpion on the second screen would sometimes jump into the ground on the side and get stuck inside).
Any news on the cartridge version? I want to try doing the whole thing in a row once I get it :)