Yeah i was reading on IGN.com in there interview that robert rodriguez didn't get time to finish all his dvd extras (he filming sin city & spy kids "special edition" dvd extras together.) Dimension wanted to get it out quickly for piracy reasons.
All you get on this 1st edition is the theatrical version, a small 6 mins behind the scenes & dolby digital & DTS soundtrack.
Later on (prob christmas or early 2006) a new directors cut with 2 disc special edition is coming out.
Read the interview
here !
I'm gutted at this and is one of the reasons i waited 4 years to buy lord of the rings!
By the way The DVD look amazing on my 37pv500.