I got the new model today. I immediately noticed differences in the build as soon as I took it out of the package. Mind you the differences were very minor, but the casing material felt different, more sturdy? The screen's colours seemed a bit better as well? The Joy-cons too felt different when I get the unit up. All these could be placebo, but overall the impression I got was, as advertised, that I was holding an improved model of the Switch.
I noticed the same things. Definitely sturdier.