Like many people, I love Gmail, Google’s powerful and free email service. I love it so much that I stopped using email clients like Mail.app entirely, preferring to direct or forward everything to my Gmail account.

Until I came across Mailplane.

Check out the above screenshot on Flickr for larger versions and comments.

For the past few weeks I’ve actually gone back to a desktop email client. But Mailplane isn’t like other email clients. Mailplane was designed to work only with Gmail as a desktop interface. This means it’s sort of like a dedicated browser for Gmail.

Why would you want to do that? Well, Mailplane has got a load of features that your browser wouldn’t have.

• Multiple Gmail account support - even works with Google Apps accounts
• Great integration with Address Book and Keychain
• iApps browser (iPhoto, iTunes and iMovie)
• Drag and drop files to attach them to your mail
• Automatically resize images when uploaded as attachments
• Support for custom stylesheets so you can change Gmail’s default look
• Growl notifications

The best feature for me is increased productivity. I find that I’m more likely to open up different browser tabs and get distracted when checking mail if I use a browser. With Mailplane I’m in email mode all the time so I’m less tempted to check football scores or read my RSS feeds.

Arguably, you could probably replicate most of the above with Firefox and a handful of extensions but as much as I love the ‘Fox, it is so darn slow.

Interested? Go check out the video intro. Or check out TUAW’s posts on Mailplane. Mailplane is currently in an invite-only beta, but I’ve got 5 invites to give away. Leave a comment if you want to try out Mailplane. Remember to use the email address you want the invite sent to. I’m going away for the weekend so I’ll send them out on Monday.