With a convenient one-bolt clamp that's tightened from the side, the Ritchey Carbon WCS 1 bolt seatpost seems to offer a more compliant ride without being whippy and is easy to live with.
Made from what Ritchey terms 'high modulus' carbon fibre (essentially, the type of weave means it's strong and compliant), the WCS has an unusual one-bolt cradle for ease of saddle fit/adjustment, greater saddle clearance and a saving of 5g - although I question the claimed aerodynamic advantages and suggest a torque wrench to avoid over-tightening.
The Ritchey Carbon WCS slots cleanly into the seat-tube and it is clear where the money has been spent. The glossy lacquer is excellent and enhances the beautiful carbon weave, and subtle red graphics make for easy saddle adjustments, though riders of semi/compact frames might appreciate the longer (350/400mm) options.
My 70kg of weight hasn't revealed any shortcomings - I haven't even needed to re-tighten the clamp - but riders nearing the recommended maximum 110kg might be less casual.
The WCS scores over cheaper models in terms of weight, finish and sizes available, and seems to offer a more compliant ride without being whippy. However, I'd stick to tarmac duties, and in-line posts, as opposed to the WCS's offset design, might better serve those looking to position themselves forward of the bottom bracket or closer to the bars.
Ritchey recalled the one-bolt WCS post in December of 2007. Updated production is becoming available at teh time of posting (February 21), but before buying one of these posts you should check the details of Ritchey's recall.