I have test drove 2. It wasn't enough for me to get rid of my 17 3500HD gasser.
I would wait for at least the 4.10s. It has more low end then my 6.0 but I think to use the extra power it needs 2 more gears and 4.10s and It will stay nicely planted in the powerband.
I went from an 02 2500HD gasser to a 2017 3500HD gasser, the two extra gears make a huge difference. Both trucks have 4.10s. I notice that certain hills were I would see 4500 rpm in the 02 I barely crack 3300 in the 17. I am sure the extra power helps, but those 2 gears made a big difference.