There are some serious bugs where people will get stuck at tables. Sometimes you can force them out, sometimes you can't. It is very frustrating to get to teh end of a day and be unable to finish because there are customers stuck at a table.
Downgraded rating because of the targeting priority problems. The impossible badge is even more impossible then it should be ghosts can just fly over anti-ghost towers without being shot at.
soup, there are some undocumented keyboard shortcuts. You can use the number keys to select towers to buy, U will upgrade and S will sell. It is still annoying, but less so.
I agree that the game needs a please don't fire on this critter option, or even just a the people are smart enough not to fire on things that absorb their attacks feature. I also agree that it would be really nice if the little buggers could walk around between waves, they are people after all.