I use a garmin ForeTrex 201 and it can display vertical speed. I find this one of the most useful measures while riding in that you can (at low speeds, ignoring wind and rolling resistance) equate vertical speed directly with your power output without a Power Tap or other torque measuring system. If you know your fully laden mass then you can infer your power to lift that mass against gravity. I know that, regardless of the slope of the road (within the gearing range of my bike) if I'm doing, say, 10 meters/minute vertical I puting out X-watts. (I forgot what 10m/min equals, but around 175 Watts I think). I know, also, that if I do 15m/min for very long I will get really tired!