If you are considering the ART Spiderjack as an essential piece of kit for 2009, Treetools recommend you talk with someone who owns one before you buy. There appears to be a real 'art' to using the Spiderjack but once mastered there is no going back. Matt Glenn has one of these babies and he'll give you an honest opinion on its performance - amazing precision, very fast - but for experienced climbers only.One piece of advice Matt has passed on to Treetools is the choice of carabiner. Make sure you have the correct shape biner or the rope will be out-of-line with the Spiderjack braking mechanism.
For example the DMM Ultra O (which is designed specifically for use with the Hitch Climber) tends to bunch the rope and Spiderjack connection into the top of the biner forcing the rope and Spiderjack into an awkward angle relative to each other. Treetools suggest using the Petzl Am'D
Triact Lock biner - the D shape keeps the rope and Spiderjack in the correct alignment for maximum performance - thanks Matt.