Well, I just got my new Black MacBook to replace an aged iBook 600. My biggest fear was that I would have to take a huge cut in Battery time.
Turns out that where I was getting 4.5 hours with the iBook ( replaced the original battery with a 4800maH battery ) I am getting ~3.5 hours with the MacBook.
Rather pleased, as my Dell from work barely gets 2 hours...far too short in my opinion.
Max.