I'm so weary of the weight because i'm only a thin light weight freak.. if i have two heavy, its too much.. where as if i have too light, i'll bounce around. Thanks so much for the feed back people!
Weight it overrated.
At 54kg my first dh bike was 22kg. My current bike is 17.5 I'm a wee bit heavier now but still a lightweight myself. Also consider where the weight is placed. A bike that's weight is low down (low center of gravity) will feel lighter, it will change direction faster, be more stable and corner better, weight placement is huge.
The new commencal as mentioned are not the lightest bikes but their weight is low the bike feels lighter and handles much nicer than you would expect.
Don't get me wrong a bike that's light is nice, it does give you a but more bounce in the rock gardens but its so minimal, the unsprung weight of the bike is small and as the rider you are the heaviest part and placed higher, your body weight would be a bigger factor and your athletic ability.
If you want to build up a light bike do so, by no means is it up to us to decide for you, if you have a dream build go for it, but don't worry about weight to the point you sacrifice performance or spend stupid amount of money (unless you have it and want to)
I like to use the example of gee atherton, when he won the worldcup overall back in 09 (I think) he was in one of the heaviest bikes in the field. We have seen riders go to the extreme only to be beaten by a rider who has a kilo heavier bike.
Weights important but not nearly as important as it appears.
Main point is dont choose a bike on weight go with the frame that will perform the best for you.