a lightweight carbon fork is sweet! carbon offers a smoother ride than alum. and is stiffer. the new forks come in about 300 grams...but that is serious money, you could find a 350 gram fork at a reasonable price. I think the key is to leave the tube on the long side...about an inch above the stem. just add a spacer there and you can always raise the stem if you need to later. another advanage to leaving the tube long is that there is less chance that you crush the end of the tube. you will save weight on the fork and stem...at least a 100 grams on the fork and another 100 on the stem.

I pull on the handlebars hard when I stand on the bike so I like a stiff stem, but thats me. some of the lightweight stems will flex. I like 3T, thomson and fsa.