I've never tasted either of the older labels of Lemon Hart: my interest in cocktails got serious only after the imports stopped. I bought a bottle of the Hamilton 151 a while ago and have almost worked my way through it, liking it a lot.
When I got home I poured a shot of each (Hamilton and the new LH) to do a quick and dirty taste test, but it quickly became apparent that these are just too hot to drink neat with any discernment. I would say that the Lemon Hart burned with alcohol less—was a little smoother—thought that may just have been because I sipped it second. But maybe that tameness is connected to the disappointment your Instagram guy felt in the cocktail context.
I'll do more testing.