I have Boris FX Red and although a great plug-in, one of the limitations of using it in Vegas is that the motion effects (stabilizer, tracker, etc) have to be rendered outside of Vegas in the Boris stand-alone (included with the software plug-in). The motion stabilizer has been a life saver for me on many shots. The stand alone Boris FX product functions as a compositor like AE. Lots of great things you can do with it. Then you can render as QT, still image sequences, AVI, or TGA still.
Haven't tried MBL but have seen Eugenia's videos and they sure look great!
ProDad makes a variety of pugins including Mercalli for motion stabilizing. I have used this for smoothing handheld helicopter footage with great results.