What's up with different suspension designs?
Rear suspension designs fall into two general categories - fully-active designs and semi-active designs. Fully-active designs are meant to work all the time - even when climbing - offering the most plush ride downhill and traction benefits uphill. Examples include the single-pivot design (Santa Cruz Superlight, Diamond Back), Specialized FSR, and the GT I-Drive. Semi-active rigs, based on pivot positions or mechanical additions, are meant to de-activate while climbing to minimize bobbing. Examples include the Giant NRS, Trek Fuel & Fisher Sugar, and Specialized Epic.
The Specialized FSR design is by far the most efficient fully-active design in the market today. The inherent flaw in fully-active designs is pedal feedback, resulting in the bicycle bobbing when climbing uphill. The FSR design transforms vertical bob to a more horizontal bob, delivering full traction benefits while virtually eliminating bob.
The Giant NRS design is arguably the least-flawed semi-active design. All semi-active designs are inherently flawed due to what they're trying to accomplish - a smooth, active ride downhill while locking out during climbs, without the use of lockout levers. For example, the Trek Fuel/Fisher Sugar design loses its suspension characteristics while braking - something you'll be doing a lot of while going downhill! The Giant NRS does lose some suspension when pedaling downhill, a small sacrifice for those who want an ultimate climbing machine at an affordable price.