Queen's Fodder is the most laggy level
At 180 blocks your entering the realm of Lag
I found that running at 70% speed on the level I got around 55 Frames with TheBlob.bsg

I believe the issue at the moment is that the game only uses a single core of the CPU, which is why utilisation is so low.

Of course there will be tweaks we can make to performance as development continues but the biggest thing for us is looking at moving to Unity 5. Moving to Unity 5 should offer us a very large performance increase. In the past there was an issue with Unity 5 that prevented us from moving over to it, but Unity tells us this has now been resolved.