The thing I enjoy about HT isn't so much in comparison to what came before or after. Hard Times is set in the decline and aftermath of the Rebellion War, and I equate that thematically with the periods following both World Wars. The Hard Times Era is the proverbial "lost generation" IMTU. The great powers that emerged and fought their destructive war which shattered the Imperium.. they all lost. Only the Solomani, Vargr, and Aslan really could claim something resembling a "victory". Which, as has been pointed out makes this Mileu dark. But it's that feel that almost makes the Hard Times a sort of "Traveller Noir" setting.
And Gods Below, do I love a nice Noir setting in deep space

. That whole idea of a lost patriotism, regardless of who you supported in the war (if anyone). This setting where nearly everywhere you go, you find that the war has touched that place. Some more severely than others. Due to the darkness of the great failures of the Rebellion Factions, the local successes, the "Human" (and Aslan, Hiver, Varger, etc..) victories shine brighter. Each small localized triumph amidst the collapse offers hope to everyone who hears of it. That's the payoff to my PCs.
The setting shows that despite no clear victory in the Rebellion War, there was no clear defeat either. There was no showdown, and glorious fall that can be romanticized as is so often done with regards to the defeat of the Confederate States during the American Civil War. Much like World War 1 in Europe, the Rebellion War ended in exhaustion. And because of that, the Hard Times has no universal villain, no universal saviour. The morality of the Hard Times, is very much grey. Which makes for some good, complex storytelling fodder.
And that, my friends is why the Hard Times is my favorite setting.