While we're in beta, we're going to be clearing the leaderboads every now and then. And then, finally once again on Friday Dec 1st (bumped from Nov 25th) (release day). This is normal. Score amounts per game may change as we tweak things here and there.
Also, new silvery-chrome artwork for the AI bots is in for Survival mode, and a less bass-punchy projectile sound (it was too overwhelming on some stereos in 3 and 4-player match-ups).