|Vertical Tabs in tree view with Windows theme|
In its current form, it provides two modes: List view and Tree view.
List view is a simple tab list in the same order as in main tab bar. Tree view, however, tracks the tabs hierarchy. This means that if you open a new tab from the current tab, new tab will be added as a "child" of current tab (for example if you search for something and then open the search result links in new tabs, all those tabs will be added as children of search results tab).
Vertical Tabs also support themes, there are currently 3 built-in themes, but you can also use your own custom theme. If you actually end up writing your own theme, don't hesitate to share it!
As some of you were asking when will the first Falkon release come out, I want to say that it will be soon. Last things are being finished now before the release can be finally made.