No offense, but I'd think it is pretty obvious that this is a proof-of-concept and any interpretation that this is in any way billed as "ready for prime time" shows a complete lack of understanding of the real accomplishment here. It also devalues what's been accomplished.
This is a MAJOR accomplishment. Like many other early stage technologies it might not be practical but will most certainly pave the way for very practical applications. You do realize that this essentially represents free energy for both powering AND maneuvering space craft, right? About the only thing you'd need with a spacecraft built using this kind of technology is thrusting mass for maneuvering in gravity wells and/or takeoff/landing from the surface of a body (looking much further out).
Certainly a number of overall technologies will need to come together for this to be applicable for anything beyond use for satellite positioning. The use of this for a space faring craft will be faced with a laundry list of other techology hurdles, such as:
1. Mass/scale engineering. What would it take to build a sail large enough to provide inertia but can remain rigid enough to actually move a spacecraft module.
2. What are the affects of long term solar radiation on the solar/lcd panels? Will they survive the hard radiation of the "solar winds" long enough to make travel worthwhile?
Another question concerns the math around the acceleration of the object. I don't have a clue myself (but it would be interesting to look into). Remembering that the solar radiation used by the sails is travelling at the speed of light we need to calculate the acceleration of the body over time. I think we'll find that even though acceleration is slow it is also continuous, so you can reach EXTREMELY high speeds over time. Here's a quote I pulled from http://www.planetary.org/programs/projects/solar_sailing/facts.html:
"The real advantage of solar sailing is that, unlike a chemical rocket that applies a lot of thrust for a very short time, sunlight hitting the sail applies thrust continuously. In 100 days, a sail-propelled craft could reach 14,000 kilometers per hour. In just three years, a solar sail could reach over 150,000 miles per hour. At that speed, you could reach Pluto in less than five years."
Pretty awesome stuff.