I still have a lifetime standard DNS subscription with them from back in the day when they were dyndns.org and you could physically mail them cash. The DNS hosting has been very solid (except for the day Mirai took them offline) but the standard query limits are way too low for any moderately trafficked website. All the managed DNS providers I looked at seem to have very restrictive query limits without a "enterprise - contact us" plan, one of the reasons why I decided to just do DNS-only on Cloudflare.
I use he.net DNS quite a lot for personal projects. I've had a few instances where DNS was not resolving that make me a bit cautious to move larger sites onto their service.
