I stumbled across this thread looking for some carbon fibre fork recommendations and at the risk of reviving a zombie thread, I thought I'd toss my 2 cents in:
We bought a Trek 7.1 FX for my wife a few years ago. Contrary to WDH74's salesperson, the advice we were given by our local bike shop in Toronto, was NOT to upgrade, but for different reasons than most posters noted here.
The salesperson asked how much we rode - at the time maybe 20km once a week, very casual riders. He said that until we hit a level of doing +50km rides (about 30 miles) or farther in a single ride, we wouldn't notice any difference with the carbon fibre forks and they'd be a waste of money. Although the CF forks lighten the bike (which he thought was meaningless to most riders) the big difference is dampening the road vibration. He said most riders don't get fatigued on rides shorter than 50km . After that, fatigue and soreness brought on by vibration becomes an issue.
Fast forward 3 years later and my wife and I are now riding 3 to 4 times a week and usually 50+km a ride (kids are older = no more running to hockey and soccer = time for ourselves!!).
Vibration fatigue has become a major issue for her. We followed the rest of his advice which was prior upgrading to CF forks, get good gloves and pad your grips. That helped a lot but she's still bothered on longer rides so I'm looking to upgrade to the CF forks. I'll post that question on reco's in a separate thread.
BTW the Trek has about 2500 miles on it and is holding up quite well.