First thing is first...the neck is a bolt-on, thicker than the Fly, and only has 22 frets. *Secondly, the neck is usually mahogany on the Nitefly and the body can be swamp ash or mahogany. *That said, it is a heavier guitar than the Fly.
Now, I think they can still be a nice guitar. *You still get the composite covered neck and the bonded stainless steel frets, which are a pleasure for sure. *The pickups, in my opinion, could use some changing. *Also, the piezo in the NiteFly is NOT the same as in the Fly...it is a cheaper version which is a noticeable difference.
I would buy a used one, because at the price you can get one for, they can make a fantastic buy.
One other thing....I have heard there may be a problem with quality control on some of these, although I have not seen it myself. *Check to make sure the E strings don't easily fall off the guitar when you are playing, and that there is no or very little buzz on the guitar.