Can I downgrade to Mavericks after installing Yosemite (beta/developer preview)? I have installed the developer preview for Yosemite.

Huge mistake. Everything in my workspace is broken.

I don't have any sort of backup image. I was wondering if I could re-download Mavericks and run the installer - would that effectively downgrade me back to Mavericks?
To downgrade, boot into Internet Recovery with ⌥⌘R and select Reinstall OS X.



With regard to the original question for Yosemite Developer Previews, yes you can, but note that Yosemite DPs so far do seem to break most of the App Store. If you are still running an early Yosemite Developer Preview, you can downgrade using the Recovery HD (⌘R) as the Recovery HD was not upgraded. For later DPs, including GM and public beta, see above.