on April 2nd the 0.2.0 was released.
It's currently stuck in the review queue at addons.mozdev.org so you need some patience. As a workaround can download a copy from sieve.mozdev.org or from sourceforge
The switch from 0.1.x to 0.2.x implies a major change. The extension got an UI. But be prepared it's not like a typical filter gui, it's more like a GUI for graphical code generators or HTML editor. It just abstract sieve grammar and syntax, so that the logic is not limited to specific patterns. You generate the sieve script by dragging and dropping atomic elements.
Currently the default view is the source editor, this will change as soon as the GUI is mature enough for everyday use. To switch to the Gui, just toggle the "View Source" toolbar button.