Rather a lot of luck involved in this game, I bought 2 upgrades, and he got to his house, at some speed, but then I get loads of upgrades and buy decent shoes, and he goes around 25,000. I know that's part of the game, but a lot of the upgrades are practically pointless. Still, I whittled away a good hour, and I did enjoy it! Probably around 3.5-4/5 :)
This is a good concept, however I also agree that it's really picky about how you put it together, meaning you spend ages trying to move everything to how the game wants it.