Do you let people beta test?

Absolutely!

Within Spaz, you can enable "check for test versions" in Preferences > Upgrades. That will tell you when more stable testing builds are available.

If you really want to be cutting edge, keep an eye on @spaz on Twitter, where we will sometime announce builds that aren't stable enough go into the testing feed.

If you're especially ambitious, you can build from source at any time.