It is a pretty cool addition to Gmail. You can easily create new emails from a wide range of templates with a single click and the signature generator looks pretty awesome. I use one Gmail account for numerous addresses so being able to bind different signatures that best represent each email and having a quick way to managing them from within Gmail feels pretty awesome. For an application still in alpha this feels pretty rad. Also the weather widget makes for a pretty cool addition to the sidebar... probably doesn't scale very high in the usability factor specifically but it is nice eye candy for an otherwise static gmail interface. Overall, I like what Mailbird is doing with the addon. Keep up the good work!