Badly needs a "retry" button. Going back to menu and then back the world is annoying if you're trying to get the "no death" portion of the achievement.
Upgrading is too expensive. 115 fuel to upgrade my New Police Boots to give it a 1% boost in speed? Unless you like to buy fuel, I just don't see how it's worth it.
By the way, thanks for the active gear update :) I'm loving it so far.
If you have a strong enough force, you can actually just let your game run, open a different tab, and then play another, more interactive game. Your units will eventually destroy your opponents castle and you'll get oodles of money. You can even do this with some caves, and you don't even have to use your spells! For instance, I have a fully upgraded force of Succubi, Heli-dwarves, dark riders, dragon riders, cannons, and centaurs, and I chose Cave #2. I just left the game running while I just went and got myself some Lunch, and when I came back I had won and I had earned 2,000,000+ money!
OK!