well, Ive played the Genz, Fender and Ampeg. Knew in 5 minutes that yeah, with enough outboard enhancements I could make any of them seem adequate, but they all left me looking around for another amp to try. Ive sat thru sets of bands I know and love who switched to Class D only to be completely put off by the lackluster sound scape they now had. Those bands had the Tecamp, and Mesa in addition to the others. I will admit, a friends band uses the Markbass and his tone and presence really sounds good and lively, and that was a real brain twister for me because Markbass has never appealed to me in any other platform. So no, Ive used none of them over "multiple long sessions, over prolonged periods of time", but thats because not a single one inspired me to want to keep playing it.
No, I wont brag that I could always identify them, just like I cant always tell which tone is the real ampeg versus a modeling platform, BUT I can tell you that every one Ive played, and every one Ive heard live (but the markbass) has left me REALLY uninspired.
look, class D has volume, and can get any tone the EQ/preamp can create, BUT.. it lacks any real palpable body and soul. When I play a tube amp its like a BIG lively red rubber kick ball bouncing into you with all the dynamic response, feel, and dimension. A good solid state amp might be more like a medicine ball. Its hefty, thick and hits ya hard and you can catch it and go "damn, thats heavy!" The class D hits you hard too, but more like you got smacked with a big piece of 4x8 Drywall. Yeah, you feel it, but it was just a one dimensional smack that just stunned you and walked away. Its kinda like the Line 6 stuff. Yeah, its got any tone you want it sounds great at home or in the store, but in real working life, Puhlease!
look, I get it, gear is big and heavy and cumbersome. If I lived in NY and had to commute from my 6th floor walk up across town on the subway to my gig, I'd probably be glad to have an amp that can fit in my gigbag and carry my 210 knowing that 99% percent of the audience isnt going to notice the difference, but I couldnt be happy with that day in and day out as my bass playing home.
if you like it, enjoy it... just please dont try to convince people that your decision doesnt come with its own set of downsides that you find acceptable and think that everyone else should too. I love tubes. I wont try to convince you that you should lug 90lbs around to sound better to just yourself, your band, and 3 audience members. Just dont expect the inverse from me.