Mailplane 3 just came out of beta, and it's great. I've been using the beta for a while, and saw stability and speed improve with each iteration.
While Gmail works great in a browser, there's something about having a dedicated application, as opposed to a Chrome SSB or Fluid instance. Mailplane actually is a wrapper for Gmail, but it's a bit like having a browser just for Gmail with access to many OS X goodies and 3rd party add-ons.
Before Google added multiple account switching, for example, Mailplane allowed you to easily switch between different Gmail accounts (it still does, and it's easier than ever using tabs). I still find this handy, although a better solution is to start using one inbox -- something I'll discuss in a future Productivity Tip.
Some notable features new to Mailplane 3:
- Google Calendar is just another tab in the interface, so it's easy to get there. Also, calendar invites link to that tab, saving you mouse clicking time.
- AwayFind (which many of the TUAW crew swear by) and RightInbox support are built in. And there's also the previous support for other 3rd-party add-ons like Rapportive, Boomerang, etc.
- As an application, Mailplane offers OS X services, Notification Center integration and AppleScript support.
- Resizing and compression of image attachments is handled within MailPlane.
While it took Mailplane a long time to get to 3, a lot of the enhancements deal with the efficiency and optimization of the software. You might not notice all the little touches at first, even if you've been a previous Mailplane user for a long time. Still, Mailplane 3 is a must-have upgrade if you live in Gmail. If you've never tried Mailplane, you can take it for a spin for 15 days and see if you like it. Personally, I think it is worth the US$24.95 price tag for an individual.
Note that there is no iOS version of Mailplane, and it will only handle Gmail accounts. Of course, you can always get Gmail to handle all of your email, but that's up to you.