What does 'Pre-Release' version mean?

If your version of dotPeek is identified as 'pre-release', you are using an old dotPeek build that was published before the official dotPeek release.

These builds should work without any limitations, however they might be unstable. We recommend that you use the latest release version, which is available at http://www.jetbrains.com/decompiler/download/index.html.