The devs say that the code optimizations done in this update have sped up and smoothened out the game, and while the framerate tends to suffer a bit when the action gets too intense it's still a definitely improvement over earlier releases.

Here's the (rather short) changelog for Apollonia v0.4a:

Code Optimisations
Explosions from tank shells hitting buildings are visible more often
Thinner air strike targeting circle
The devs also note that a new issue has apparently showed up in Instant Action mode where everything except the HUD turns white. They've only encountered it once, though, so it may take a bit of testing first before this can be remedied. Heck, you may not even come across it at all. If you do, let them know via the forums.

Downloade Link: http://www.sendspace.com/file/46pm3c