Frontal area tools help a lot in refining a position.
(I'd note that my opinion may be a little biased as my company offers similar software - velogicfit 3D Aero).

The main advantage comes from eliminating guesswork - it usually turns out that just trying to get lower and narrower (to be like Tony Martin) in one session will not be the fastest option.
Combined with 3D Motion capture you can more easily find the balance between appearing small to the wind and being stable on the bike.

I don't know of any free equivalents (I have looked). The cheapest way to get access to this kind of thing is to find a Kinect for xbox one and just subscribe to our software for a month or two.