I'm not sure I would call it an error, but I've noticed that if you have your inventory up, you can heal your characters while the game is paused. Seems like a cheap trick.
Found a glitch - At the end of a level, if you press the space bar before the end screen comes up, then click on the "Next Level" button, you skip a level every time.
I would love to see an upgrade for money collection, ether as an increased draw radius and speed, or possibly as upgradable minions that collect money for you - the latter would negate the hotkey issue for powers.
You can grab the two halves of the soundtrack at billkiley.bandcamp.com and store.flashygoodness.com !