Strengths: Low weight, very rigid (no grinding against chain on high pressure pedalling), generally easy to fit (see notes later). Tools and bottom bracket all included. Excellent front shifting. Welcome change to Micro drive format for XTR with associated benefits.
Weaknesses: Expensive. The fixing bolts for the left hand crank need to be accurately tightened. I have heard about someone undertightening them and it fell off/stripped the spline (£££ouch!). First shipments came without instructions (my shop got me some info from Madison). Also, Shimano specify a tighting torque for a HAND gripped (non wrench) tool (supplied) - excuse me while I adjust the torque meter on my right bicep....
Overall: An excellent, well developed product with good looks and innovative design - if borrowed from the old Bullseye design! But Shimano always do that (V brakes were first introduced by Marinovative, etc etc). XTR is expensive, but I find that it outlasts other groupsets by several magnitudes and really does perform better.
Strengths: Low friction shifting, consistent performance in poor conditions, reduced need to change rear outer cable. Improves performance of any grade of rear mech.
Weaknesses: Need to trim outer cable very accurately for optimum positioning/performance of device. (Best to fit new cables at the same time to maximise short/long term performance). As the inner cable forms to the tighter bend - albeit friction free - the rear mech cable adjuster will need slight tweeking for several rides.
Overall: Imagine Shimano just upgraded XTR rear shifting - that's the advantage this device brings. When you consider the design, all the component parts and assembly, its good value really. Consider how much you would have to pay for a higher level rear mech/shifters/quality cables to attain a similar shifting performance upgrade. Buy one.
Strengths: Decent trail reviews, varied, multi bike tests, head to head eqt reviews, good source for shoppers.
Weaknesses: Reviews often clearly not undertaken by people with sufficient engineering background. will often pad out reviews with really subjective, useless comments regarding stiffness, feel or traction. You can just tell they made it up to write the review. There also seems to be bias towards certain brands and technologies, that are by no means universally held beliefs by knowledgeable riders that I know. There is an obsession with a 'praying mantis' upright riding position and riser bars, when often a SEMI stretched position is best for all round riding. How often do you read, "we would change the straight bars for risers".
Overall: I buy it regularly because it is the best of a bad bunch. Why does'nt someone with good journalistic background, mountainbiking and engineering knowledge start up a mag that is objective, truly analytical and accurate?!
