I just started this game back up today and had forgotten how much I love it. Super addictive, and trying to beat the top online scores makes for a fun and sometimes frustrating time.
Anyway, checked the leaderboards and the player at number 1 has 1.3 million points on the same level! How the hell is he doing that?! Would love to see some videos of people getting these types of scores.
I know I'm about a year late on this, but the best tip I can give you is to take the larger enemies down to just a sliver of health, then lure some of the smaller enemies over, and take the big guys down immediately after a small one. If you watch the multiplier gauge underneath your score, it shoots up to max and then drops back down super fast... so you want to pop those big guys as soon as possible after killing a less valuable one.
In arcade mode, the "money/points" items work the same way, so get right next to them, shoot a small orb, and then immediately grab the item.
Another good one is to put your satellites directly in front of the main ship for higher accuracy scores. I can get about 90% on Epsilon 1 consistently by doing this and shooting in small bursts.
Since you wanted to see a video, here is (a kinda crappy) one that I shot with a camera back in February:
http://www.youtube.com/watch?v=CCn-KXRj7e0
My scores have gotten bumped down quite a bit over this past year, but after a couple hours playing the Epsilon Cluster on single player tonight I recaptured the top USA spot and 5th worldwide. Still got some room for improvement too since I only got 2 bonus rounds and each one was only in the 40-50 second range. Going to try and get back up there on the other levels this coming month, and I have a capture setup now so I'll take some better vids.