Apple has seeded the first build of OS X Mountain Lion 10.8.1 to developers through its Mac Developer Portal. Interestingly, there are no known issues despite it being the first build, so we'd imagine that the 10.8.1 update will be released to the public in short order. Apple has focused on improving Active Directory, Microsoft Exchange in Mail, PAC Proxies in Safari, SMB, USB, and WiFi and Audio when connected to the Apple Thunderbolt Display for the first Mountain Lion update, which weighs in at just 38.54 MB in size. If you haven't upgraded yet, you can download Mountain Lion from the Mac App Store.