My turning point in switching to clutchless upshifts was an article in either Motorcyclist or Sportrider a few years ago. As a matter of fact, you put less strain on the tranny with clutchless upshifts. Reason - upshift occurs automatically at the moment the transmission is unloaded. As a result, the grears don't bang each other too much. Again, rpm match is automatic - otherwise, upshift will not occur. I think the reason clutchless upshifts are possible because momentary throttle roll off unloads transmission and matches rpm at the same time - when this happens the preloaded shift lever pushes the gears together. Another benefit of clutchless upshift that it is quick and clean - almost like an automatic tranny. So, I've been doing clutchless upshifts for years now with rare exception. Would never go back. There is no such thing "you have to know how to do it" - simply understand, practice and you know - that's all there is to it. It is actually simpler than the clutched one.
I mean how hard it is doing the following while zooming along: preload the shifter (don't worry it won't shift while tranny is under load), blip the throttle off and on (shift occurs fully automatically), unload the shifter. The only things which takes a bit of practice, when you blip the throttle off-on, you should bring it back on slightly less because you are now in a taller gear. How much less depends on what gears you are switching. For example, in the case of 1->2, you would have to bring the throttle back ON noticeably less because 1 and 2 have very different ratio. In another example, if switching 5->6, you roll the throttle back ON almost the same because the difference in gears 5 and 6 is minimal. In any event, if you mismatch your throttle action and feel the jolt of the bike, the gears are already locked in the new position and don'g bang on each other, so it is no different as if you accelerated suddenly, or closed the throttle suddenly - your chain will feel it (and it is fully able to withstand it).
During clutched upshifts, it's difficult to match rpm, so even though the transmission is unloaded, the gears bang on each other most of the time because of rpm difference.
Downshifts are clutched most of the times. Clutchless doesn't work well because in order to unload the transmission you would want to roll off the trottle momentarily, but in order to match rpm one would need to roll the throttle on more. Can't have both at the same time. So, clutchless downshift would work when downshifting from 6->5. You can unload the tranny, but the difference in rpm between 6 and 5 is not too bad, so you can get away with it - more as an exception; and the higher the rpm the more it would be a bad idea to use clutchless downshift. Also, the bigger the difference in rpm between gears, the worse it is for the tranny. So doing 2->1 or even 3->2 - probably not a good idea. I also think in real life there is not much need for cluchless downshift - most of the time you downshift when you are slowing down, so there is plenty of time.
I think an additional benefit of clutchless shifting is if your clutch stops working after going down for example, you can still ride the bike to get where you need to be.
