Apple has pushed a new iOS 5.1 beta build to the platform developers for testing. This update is meant to address the iPhone 4S battery drain issues more seriously and also fix the bugs with virtual assistant — Siri. Do note that Siri is still in beta phase and several issues would exist. 
Notably, iPhone 4S adopters have been complaining about the battery drain issues and Apple did release the iOS 5.0.1 update to fix them. However, the battery drain issue continues to persistently haunt the Apple Software engineers.
Apart from that, the iOS 5.1 beta includes several underlying bug fixes. Currently the iOS 5.1 beta is in testing phase and might be released sometime early next year.
The iOS 5.1 beta build will continue to stay under beta testing with registered Apple iOS platform developers till early January 2012. Till then, users may have to cope with the existing issues with the iOS 5.0.1 running devices.