It’s a simple idea: take the minimal interface and make it available (faster) on the desktop, to dash off quick messages and keep an eye on your inbox (or other important folders). Because it’s so small you can pop it into a corner of your screen and keep working. While Wave is getting its feet, it also saves you dedicating a tab to it while letting you participate and build up the community.
Unfortunately because it’s simply a view to the mobile interface it suffers one of the same beta flaws - it does not sync changes until you click “done”. So if you’re used to the behaviour of the regular wave interface, you might find it difficult switch back and forth regularly. Additionally, none of the keyboard shortcuts from the main interface work, so you need to mouse around a lot more.
If you need a simple interface to use Wave, Waver might be for you,