I could argue either way. I used to never think they were worth it until I just bought one. I was looking for a 2003 Premier and Grizzly sports had a blem DNA for $300! The blem biolite board was $280, so I said why not. I have always been a fan of the Premier, my cousin has the 2002 Biolite, but there is definitely a noticable difference between a biolite core and a DNA core. I don't know what they were made of a few years back, but they are made out of balsa wood now. Everything about that board is more responsive. It does feel a little looser, but after having ridden it a half a dozen times now, I absolutely love the board.
In my case the difference was only $20 for a blem board, which by the way is the only way I would recommend buying a board, I can't even tell where the blem is without searching hard for it. But I am a firm believer that the DNA core boards (at least by Hyperlite) are definitely a step up.