One thing you could add, is a permanent upgrade to your turrets in rp upgrades. Maybe a 0.1 Times multiplier? Just something like that.
I think the reload speed upgrade on the Gunshot is to little of an increase for the price of the upgrade, and the price increase for the lazergun speed upgrade is too high too.
Ok, I'll have to try steam then, I was just using wine for the windows download that I got from here.
Edit: I can't download it on steam, whats going on?
Is there by any chance an unreleased Linux version?
If not, many people might like that, Linux is getting more and more popular, and wine does not always work to well.