I admit that I haven't been following the news for Nexus doing this, and it came as a surprise after coming back for mods after a long time.
A very unpleasant surprise.
While I appreciate the hard work going into web design, I still think the new layout is horrible. (And I actually have to access the old site for some mods that say "hey, would you like to donate?" because I can't find a way to download it without donating. Donating is good, forcing to donate is not).
For one, I have a wider screen than I used to, and the site stretches way too much to be comfortable for me. The images are too large. I suppose this would look very good on a phone, but I don't browse Nexus on a phone, and I never will, simply because I don't use internet on a phone unless I absolutely must.
I would personally prefer if it was optional to switch to the new style, but as some people have pointed out, that would mean keeping two copies of the same thing running. I'm sure in time I will get used to this change, but it doesn't mean I like it. At all. It will likely mean I use Nexus less, because it's nearly headache-inducing.
Anyway, that's how I see the whole thing.
Edit: forgot to mention that for me the new site is much slower to load.