In answering Mark's original question, I have to agree with Gibsonj and flipflopman's generally positive assessments of the 106 which both offer more technical detail than I ever could without reference to notes. As a Jag pilot with over 2000 hrs on the jet and a fair amount of time with the 106 I have to say that as far as I was aware, the vast majority of the Colt guys thought it was improvement on the old 104. We knew from the outset that we weren't going to delivered bags more thrust for all the reasons that have been laid out in previous comments - predominately driven by the requirement to derate the engines on to provide the 'spend to save' financial justification for the upgrade. I think I can recall 2 fairly significant rear end issues with the 106 (already covered) but as both happened to 41 sqn aircraft which were both being flown by QFIs at the time the problem may not be entirely down to the engine. I don't know what the 106 serviceability stats were but I suspect that (excluding bird strikes) the Jag sooties spent far fewer nights away recovering sick jets than their Harrier or Tornado mates.
No surprise to see that Bob the Viking's still skiving off during the working day!