No personal experience of changing them but the tyre fitters I've used all curse them, as mentioned above they have very stiff side walls. On a cold winters day at the side of the road you would need to be very good to change a tyre/fix a puncture. I'm sure it can be done but I would hate to have to try myself.
On the plus side if you ride 100 miles of twisty roads at high speed and the bike feels odd you may, like I did, subsequently find there is only 10psi in the front tyre but it stayed on the rim and kept me shiny side up.
Damn good tyres if you can live with the compromised wet grip, noise, and vagueness in high speed corners caused by the blocks flexing.
Any tyre with off road ability and a high mileage capability will need some respect in the wet.