The demo now has a difficulty setting, allowing you to set the enemy spawn rate. The range is very large from 4 times slower for a super easy 'story mode' difficulty to a 2 times faster 'impossible' difficulty.
There is also a fix for some crashes that happen when ending a mission (exit, fail or success). They are very hard to reproduce, so its more of a 'hope its fixed' than a real fix.
Enemy buildings take damage from missiles more easily.