Hats off to Apple and its developer for releasing update version of iTunes 10.5.1 Beta for Mac and Windows free after releasing the iTunes 10.5 final version. If you loves to access update version rather than older simply update iTunes version to 10.5.1 as well as you can download iTunes 10.5.1 free directly from Apple Dev Center.
Just read out the iTunes 10.5.1 release note:
iTunes 10.5.1 beta 1 includes several performance enhancements and bug fixes, and is a required update for all subscribers to iTunes Match beta. iTunes Match is not included in the iTunes 10.5 GM release
Your iCloud libraries will be deleted at the end of this beta.
Backup regularly and do not delete the music you add to iCloud from your computer. Apple may periodically delete all iCloud libraries during the beta period. This will require you to scan, match, and upload songs again. Also note that some of the features and optimizations of iTunes Match may not be available during this beta.