Long ago and far away a woodworking friend from Europe impressed me using a jigsaw under the clamped workpiece. That saw had a roundish pad over the blade and a barrel grip. He supported the jigsaw with his left palm and guided it using the barrel with his right hand. This way he could see the line he wanted to follow and hardly any dust got in his way.
I practiced with his coaching me, and have continued using my jigsaws that way for 50 years. I own a Trion PS 300. I do not remember when I bought it.
I was in Europe and the UK when the Carvex PS 400 was introduced. Later I was back there after the improvements to the Carvex were introduced. Subsequently I have used the Carvex many times, including last Friday, 8 April 2011 at The Festool Store in Palm Desert, CA USA.
I can see that it is not always practical to clamp a workpiece in such a way there is room to use a jigsaw underneath, although so far this has not been a problem for me.
What impresses me with the NA version of the Carvex is the outstanding view of the cut, enhanced even in sunlight by the strobes. Although I have not pre-ordered a Carvex, two of the cabinet makers working for me have placed their pre-orders. One prefers a D-handle while the other wants a barrel grip. In both of those cases the new Carvex will replace virtually worn-out jigsaws those fellows have owned for years.