Really cool idea! Nice to have a mix of units with different strengths and weaknesses. I liked experimenting with different layouts, and the trade-off of a treasure room for units later vs. units is cool.
I had a lot of trouble getting past the first few rooms, even a room full of demon warriors, or mixed warriors archers would get overrun.
I also wish the monsters came out faster – It felt there was a lot of time just waiting for them to advance up to the boss. (I ran into this problem in my game too, not sure the best solution, I added speed-up controls)