Endless mode is awesome and all, but I would kill for a Freeplay mode..unlimited waves, but limited money, yknow. Endless mode has challenge. Also, I would advise changing the Upgrade Building hotkey in game, because when you mouse over Upgrade Building in game, it shows a 6 or a P.
Doctor: "Yep, there is blood in your stool, Mr.Donald." Donald: "And the fact that my stool is a freaking cheeseburger? What do you have to say about that?" Doctor: "Thats probably not normal" Donald: "Ya think?"