(Update: The researcher at UT, Brian Korgel, co-founded Innovalight but is no longer with the company, so some of the commentary below is mis-aimed.)
Disregard for a moment that this isn't a new idea -- among its many other proponents are research teams at the New Jersey Institute of Technology and the UK's University of Warwick. And solar ink that can be "printed" onto surfaces is already entering use.
The first problem with what UT is saying is that its current prototypes are only one percent efficient at converting sunlight to electricity. Multiplying that efficiency 10 or 15 times over in a period of three years would be a Herculean task.
Unfortunately, it's a task Innovalight doesn't appear suited to. The company, which this Wired story manages to make sound brand-new, is a couple of years old, and has been working on its ink-based process the whole time without much result. In late 2007, it was claiming it would have a 30,000 square foot manufacturing facility running within a year.
It's a devilishly hard technology. But even if they hit that magical 10 percent efficiency that might allow them to start manufacturing, the picture still isn't clear for a spray-on solar panel.
For starters, it's probably not going to be a product you pick up at Home Depot and start coating your house with. Surfaces have to be prepared, distribution must be even. And there are the little inconveniences of solar power -- like having to hook it up to the electric grid. That's easier than it used to be, but professionals still have to do the job.
Meanwhile, any spray-on product would be constrained by the same necessities of a solar panel. It would need to be facing the right direction (preferably southward, if you're in the Northern hemisphere). To get maximum efficiency, it would need to be at the right angle, not just laid indiscriminately on a wall or flat rooftop.
Finally, there's no telling how long such a product would last -- solar panels, protected by glass from the elements, get 25 years or more. Paint, as most homeowners are aware, doesn't always weather so well.
With prices dropping precipitously for solar panels, it's unlikely, at least in my mind, that anything like spray-on solar will have a chance without another decade of research. There are some interesting applications, like solar ink layered into a clear window. But for now, solar-in-a-can is a long shot.