Hot on the heels of the iTunes 10.5 release to the general public a few minutes ago, Apple has also seeded iTunes 10.5.1 beta to developers.
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 which is not included in the iTunes 10.5 GM release…
The latest beta release is available from the iOS Dev Center. Unless you’re a developer, there is no reason to download iTunes 10.5.1 beta, which by the way is safe for jailbreakers.