Last weekend a new "cutting edge" update was released: 1.55. It supports both Gmail 1.0 and Gmail 2.0.
Using Gmail 2.0 is a joy: I really like
- the "update conversation" feature;
- the mark as read/unread keyboard shortcuts;
- the speed improvements;
- and the colored labels
If you can't wait and you like to try and test it, you can enable "cutting edge" updates in Mailplane's advanced preferences. Then do a normal "Check for updates" to get the latest version. But, there is no need to rush it. When it is translated and stable it will be released to all Mailplane users.