I’ve just upgraded to the 4.0kg from the original 3.3 and the new hinges are very stiff. One-handed opening is a lot more difficult, but not impossible.
On the plus side, the whole laptop feels more rigid, especially when I walk around with it, and I have a much better range of screen angles. There’s also little to no resonance while typing.
My old hinges were very floppy and I like the new feel, but it’s a matter of personal taste.
I like this suggestion of mixing and matching hinges to get something you’re comfortable with.