Sparrow is pretty good lightweight mail client for the Mac. However, it's becoming bloated pretty quickly. I'm referring to the new facebook integration and future integrations that I'm sure the team is currently working on. I really wish there was a way to "stick" a (gmail) label on the left (black) bar. I hate having to click on a dropdown at the bottom of the bar to get to my labels.

The most annoying thing I've experienced is the fact that Sparrow takes you to the Mac App Store's website when clicking on the "Update" button that prompts you when you open the app. You cannot update or install via the website, so you need to open the Mac App Store app (redundancy there) and install it from there. That's pretty annoying. I understand that part or all of it has to do with Apple's updating procedure, but I think it's retarded. Why can't the app update on it's own without having to load the Mac App Store app???

http://sparrowmailapp.com/