I might not be too helpful but...
I just got an ibook 600 dvd. I deliberated long and hard and basically came to this conclusion: For what I use my computer for, light dv work, mp3's, internet and word processing I don't need to spend an extra 700-1500 dollars on the top of the line. Then I thought some more and came to this conclusion: I truly believe that in about one year, maybe two or three, computers are going to be so much faster that even the slowest models will be fast enough to handle any large and sophisticated programs that I could ever hope to use as a "non professional". Sure there will always be larger and more sophisticated applications demanding ever greater power, but the baseline for computer performance is rapidly approaching a point where anything extra will truly be "for professionals only". Stuff that I wouldn't use under any circumstances. I feel that up to this point, this hasn't been the case. Even today I feel that a computer such as the new tibook 667 is still within the practical range for the average joe who simply enjoys hacking around with digital video and music, etc. The real reason I can't bring myself to purchase the current top of the line 667 is my belief that in a very short ammount of time it will entirely outclassed by something so far superior that right now it's not worth spending the extra money on something I will absolutely want to replace in such a short ammount of time. I know... people will say: "but if you always wait for something better to come you will end up waiting forever since the technology is always improving". My reply to this is simply to reiterate what I said above: (sorry this part is redundant) In one or two years even the baseline computers will be fast enough for any application I could ever possibly want. So, in one year when these "new" computers come out, I will be more inclined to go out and buy the top end but for this inbetween period I don't feel like I need to waste my money on something I will be getting rid of soon so I will stick with the cheaper ibook as an intermediary solution. It's still a solid machine and it will serve to tide me over.