What do you do with it, I'm guessing it has a high resell value.
I think only the bigger pieces or maybe ones that are agatized or opalized are valuable.. the wood from the area Cy referred to has brilliant colors. I use it mostly for show, like on the patio and stuff. Mostly it gets me out doing something on a regular basis.
Arizona petrified wood is some of the most colorful anywhere.. a trip to Wyo's 'Blue Forest' to hunt is on my list, the wood isn't as colorful but unique in it's own way.