In a post on the company’s official community forum, a Sony Xperia rep indicated that the new updates had been put out to fix networking issues with these phones.
We have received isolated consumer complaints about network selection issues for the products Xperia™ U, Xperia™ P, Xperia™ sola and Xperia™ go in connection with Android 2.3.7 SW version 6.0.B.3.162, successfully resolved by re-starting the phone.So hopefully this update fixes any issues that Xperia P, U, Sola and Go owners may have been experiencing. And with this bug fix out of the way, we’re sure they’ll be hoping for a swift update to ICS later this quarter.
Further optimizations of the network selection procedures were made and affected consumers are recommended to upgrade their handset SW to a new Android 2.3.7 SW version to be available from early August onwards.
Source: XperiaBlog, XDA, Sony community forum