I'm liking it, but I wouldn't say it's made it more difficult. I've had to adapt the way I play, which I've enjoyed - investing in survival (for food) and barter (for the pack rat perk), which I've never done before. I've also thought more about where I'm going to take companions, and I'm finding that Boone isn't my favourite companion in this playthrough, seeing as he's fairly svcky at holding his own when you're in enclosed spaces with enemies at a close range. Normally it didn't matter at all, but now I make sure I've got Veronica if I'm going inside a cave or something.
The weight has been fun to manage too - I haven't got the pack rat perk yet, but I'm always collecting junk for crafting so I have to decide what to take. Plus, normally I'd carry a crapload of guns and enough ammo for an army, so deciding which 3 guns I'll take has been interesting, and I'm making much more use of the reloading bench than I did before. I barely touched it when I was playing without hardcoe mode.
I'm finding that instead of making it harder, I'm forced to think more about what I'm doing and make more use of the resources that are in the game, which in turn makes me appreciate them more.
I wish I'd started off investing in survival though - I'm way behind on that one and really wish I wasn't now!