... the sensor is in the gear box ...
And for me prone to failure, which for an item with no moving parts is pretty disappointing at around 50,000km. A reasonably straight forward replacement, but fiddly with lotsa parts to remove and re-fit to get access to it. Probably less fiddly if you have tiny hands.
It was the $130 (as I recall) bit that hurt the most.
Speedo and odo accurancy - pretty much like others have stated. Accuracy doesn't worry me, as the GPS speed display is accurate albeit a bit small. I also have a free App on my iPhone which is accurate and LARGE, with some additional handy features such as average speed, maximum speed, distance, elevation (instant, max & min). Most of these are stored in a log, but I don't really use that except after a bicycle ride,
Fuel consumption - generally around 6 litres / 100km, best around 5 (riding like a pussy), worst around 6.5 (using plenty of throttle in the twisty hills), apart from around 7 (when towing the Elite camper trailer).