Initially I was a bit skeptical about Next.js, but nowadays I really like this all-in-one experience. There are still some rough edges, but it's understandable given the scope of this project. I'd love to see more focus on TypeScript, integration with something like esbuild or Snowpack or maybe even a Deno version (there's already Aleph.js). What may not be obvious at first glance is their dedication to solve those little, often difficult problems on the web. I like their next/image component. I was surprised to see AMP support. Their approach for blending frontend with backend is not only interesting, but practical. The future will be interesting for sure.
Contrary to other commenters, I find Next.js docs pretty good. You can see there was a lot of effort put into writing their tutorial. Rough edges are mostly related to everything that supplements the framework, i.e. 3rd party libraries. I think eventually they will be expanding to cover these various scenarios.
Also, I'm working on a 12-week video course about React.js / Next.js. When I noticed this announcement on HN, I figured it could be a good way to promote it. ;) It's not yet ready (early WIP). I plan to finalize details next week. So if you're looking for a React.js/Next.js jump-start, check it out at https://reactnextaz.com