There are growing indications that the build of Froyo that was leaked was not meant to be installed on consumer devices. Apparently Google has confirmed that it was not 'feature-complete', and was never meant to get into the hands of consumers' nexus ones. This is why people are seeing errors with the market, with certain features not being there, etc. What's unclear at this point is if you'll be able to upgrade to the official Google release of Froyo for the Nexus One if you're running FRF50, or if you'll have to downgrade.
[Update] Froyo May Have Been Launched Prematurely | Android Phone Fans
engineering software | Quietly Coding
[Update] Froyo May Have Been Launched Prematurely | Android Phone Fans
engineering software | Quietly Coding