Tabbed Browsing - definitely. Now if it just had a better browser to run against.
Other than that, it's got a lot of items going for it - highly visible power meter, docking Today plugins inside its tabs, handy shortcuts for frequently used apps, the much needed "Close" function to replace the default "minimize" (yes, to any MS team members reading - if there are this many variations of "close" apps - we probably want that built-in to WM's OS
), the list goes on.
Great app and SPB really seems to do a good job making simple, practical apps that just work.
-Pete