I'm getting a lot of questions from folks, via Twitter and other venues, regarding Windows Management Framework 5.0 - which is where PowerShell v5 comes from. It's awesome that people are installing v5 and kicking the tires - however, please help spread the word:
- v5 is a preview. It isn't done, and it isn't guaranteed bug-free. It shouldn't be installed on production computers until it's officially released.
- v5 doesn't install 'side by side' with v3 or v4. You can't run it with "-version 3" to "downgrade." Now, v5 shouldn't break anything - something that runs in v3 or v4 should still work fine - but there are no guarantees as it's a preview and not released code at this stage.
- Server software (Exchange, SharePoint, etc) often has a hard dependency on a specific version of PowerShell. You need to look into that before you install v5.
- After installing v5, you might not be able to cleanly uninstall and revert to a prior version.
Generally speaking, v5 should be installed in a test virtual machine at the very least, not on a production computer. It's great to play with it, and you should absolutely log bugs and suggestions to http://connect.microsoft.com.
This situation will be true for any pre-release preview of PowerShell or WMF going forward. "Preview" is the new Microsoft-speak for "beta," and you should treat it as such. Play with it, yes - that's the whole point, and it's how we get a stable, clean release in the end. But play with caution, and never on production computers.