A comparison between a null-layout and a FlowLayout. I think (like Roberto said already) you will loose some points for GUI for using it, because it's hard to maintain, more code, less flexible,... Adding an extra button will lead to a lot of recalculation you have to do.
Indeed, that's a really funny video And it has a bit of truth in it: with GBLayout you will end up with more code than null layout (every time setting the GBConstraints). But i think making changes to your form (adding a label, field,...) will be easier and faster though then when you have to recalculate everything.
GridBag may be powerful but it surely needs whole bunch of constraints which can make "junior" programmers hard to follow. Remember one thing Sun examiners look for is "clarity and maintenability" .... so keep it straightforward.
I don't see why you need to use null layout. For me, I used BorderLayout, FlowLayout, and at times GridLayout throughout my GUI code. As long as you manage to place those components at the right places no fancy or gridbag layouts are needed.