I got one as a gift a few weeks back and am trying it out. If it hadn't been free, I'd never have gotten it. The starter pack of seeds (thyme, basil, and chives) are coming up. They sprout and grow pretty quickly, but seed packets are $20 (as opposed to like, what, 80 cents from Burpee?), you have to replace the bulb every six months which I'm sure will be 20 bucks or more, it runs constantly and therefore uses power (including 17 hours per day with the light on), and the unit itself starts at around $150.
And I'm sure my neighbors now think I have a marijuana grow thanks to the light always being on
For what it costs to get a couple months' worth of herbs, I don't see it as being worth it. Unless it outstrips my expectations by quite a bit, I'll probably shelve it after this crop is finished. For the price of the light bulb and seed pods, I can plant rosemary, chives, parsley and basil in a couple of small pots. They'll come up every year, need almost no maintenance except for occasional watering during a dry spell, and I'd still have money left over to buy the steak and potato to use them on.