In my opinion, GPU computing is significant because I--as a grad student--can easily afford a machine that allows me to perform a simulation like the following in 40 minutes instead of a whole workday. That's why.
If you're curious, this shows the density of a vortex shedding flow behind a square obstacle at Re=100 and Ma=0.1. The attentive viewer may notice a sound wave at the beginning as the system settles from uniform flow to flow around the obstacle, as well as the passing of a gentle density "nudge" intended to throw the system off balance and accelerate the onset of shedding. This was computed using my Discontinuous Galerkin solver hedge on an Nvidia GTX 260.
This work owes a lot to Hendrik Riedmann from IAG, Uni Stuttgart who wrote the initial version of the Navier-Stokes operator in hedge.
(Btw: did you notice how the movie cleverly avoids the typical criticism of being "CFD"--colorful fluid dynamics? :-)