I've wondered about them too... from all the research I've done on-line, it seems like quite a few people complain that its not really that easy to see the lights on the fretboard when you're playing the guitar.

The concept is good, and they've really stepped up their game in terms of how much material they offer now. I think the guitars themselves don't sound all that great. If I was going to go for it, I would go with the absolute lowest priced base model they offer. I don't think the more expensive models are worth it as I just don't think they'll be a guitar that you'll get into as far as tone goes.

I really like the idea though. There's tons of material based around the concept of the getting you to visualize scales/chords/notes on the fretboard, and the fretlight does exactly that, so its a good idea. It does have its limitations though. For instance, playing a song a full speed, it may be difficult or even impossible to follow the dots as they move around, and it can only show you positions, not bends, hammer-ons or pull-offs. Still, might be worth a shot.