I bought a pair of specialized carbon comp mtb shoes this weekend and used them for the century that I did. It's amazing, the amount of stiffness and power it allows me to get to the wheels, especially up hills, compared to my specialized sonoma's.
The only thing I didn't like was that they didn't have the higher end one which was only $30 more that had this click ratchet system to tighten the shoe while you're riding.
How long do you usually wear your shoes for? I've had my sonoma's for about a year and I feel guilty retiring them.