Sparrow email client for Mac reaches 1.0, lands in Mac App Store
Sparrow 1.0 does have its drawbacks, though. It still only supports Gmail (and Google Apps email accounts), which might be a dealbreaker for some. Anyone who's not using Gmail should wait for version 1.1, which will reportedly add support for all IMAP accounts. The $10 pricetag is reasonable for what you get, and anyone using a beta version will find it worth upgrading for the performance improvements and Gmail label support.
One little quirk to be aware of: if you have a beta version of Sparrow installed, you may need to delete it or move it out of your Applications folder before you can buy Sparrow 1.0 from the Mac App Store. Otherwise, the App Store will think you already have the app installed.