A minor update to Mail.app competitor Sparrow was released today. Sparrow 1.2.1, available through the Mac App Store, provides fixes to a number of crash-related bugs, as well as some changes to default app settings.
According to the release notes, the Facebook wall post option is now unchecked by default, and the inbox bar is hidden by default as well. There's also a new way to expand or collapse all messages in a conversation thread by Alt-clicking the top message.
Be sure to read TUAW's full review of Sparrow 1.2.