The reduction in rake will increase the trail slightly slowing the steering. Key word here is "slightly" - I doubt you will notice the difference. A bigger factor is trying to match the fork length. Carbon forks are typically longer than lugged steel forks so when you install the new fork it will raise the front end of the bike some which will further slow steering. It's all a mater of degree and again you may not notice. If you do decide to go forward with the fork swap I suggest that you try to find one that's on the shorter side of average to ward off any issues.

http://www.sheldonbrown.com/rinard/forklengths.htm

Good luck.