I had the 9.0 for a while. Great head. I've also had the 6.0, Neo-pak and GBE 1200.
I have said around here many times that the Neo-pak was my favorite gigging head from Genz. The lower wattage allowed the power managment to kick in at lower volumes and gave it a great feel on the gigs I do. Mine had the 2ohm mod and it worked great with multiple cabs also. I really loved that head.
Without being able to do a direct comparison, the 6.2 I now have is more like the Neo-pak in terms of feel than any of the other heads I've experienced. I know Red Planet called the 9.0 "gooey" or something like that, but I never heard that at all. It felt punchy and quick, and turning up the gain only seemed to begin adding overdrive, and not tube feel. Same goes for the GBE. The 6.0 was the same, but the thinner bottom voicing took it even further away from a tube-like feel.
I'm not sure why the 6.2 has a more forgiving, tube-like feel to it, but it does. My first thought was the 3DPM, but it seems to have this character at lower volumes also. It's not nearly as extreme to my ears as the Streamliner, but defintely warmer and more "give reactive" than previous Shuttle models. Not sure why, but I really like it. It's still punchy but with a bit more warmth on the transients. I think it's more than just the voicing change also.
Hard to explain. If the 9.2 is like this also, I personally think it might be a worthwhile upgrade for many folks. It would be subtle from the perspective of the listening audience, but for the player on stage who is standing right in front of their rig, that subtle difference can mean a lot in terms of inspiration and enjoyment.