For over ten years, I have been riding on the same Specialized BG Sport mountain bike shoes. Over time, the shoes have gradually broken down, finally warranting their retirement. As cycling shoes are your direct power connection between your feet and the pedals, you don't want to be losing energy to sub standard flexy shoes.
Aside from cost, the main differences between carbon and plastic or nylon soles is stiffness and weight. The majority of all cycling shoe soles at the high end of the range are now created from carbon fiber or a combination of carbon and composite. Carbon offers a very stiff, light platform that translates to better pedaling efficiency and control.
The new Serfas Krypton women's mountain bike shoes are stiff yet walkable, SPD compatible, with deep forefoot lugs for hiking and a nice wide toe box for extra comfort. An easy release buckle system makes theses shoes very simple to get in and out of without having to adjust the velcro straps on your forefoot.
Serfas rates their Ultra Stiff Carbon Plank sole at a stiffness level of 10, similar to their top of the line road shoes. I have definitely noticed the stiffer sole in terms of less foot and leg fatigue but do they make me faster? I can't say.
I was originally worried that the increased stiffness would mean harder walking in those hike-a-bike situations. The Krypton definitely left me scrambling to climb up over steep rocky and muddy terrain, but this could be remedied by adding toe cleats to the pre-drilled sole. I hope to not hike much in my mountain bike shoes, anyway.
Bottom Line: If you are looking for carbon fiber performance but at a more affordable price, check out the Serfas line of mountain bike shoes.
The Serfas Krypton women's mountain bike shoes retail for $180 and will start shipping in January.