It's a little underground relative to the total number of switch users in the world, but the DNS itself has existed since week 2 of the Switch's life. I'm sure Nintendo has patched accessing the browser this way as much as they see fit already (removed video, added timeout, small bugfixes, no cookies).
In terms of usage, there's usually between 500-1000 users online using the DNS at the same time, and live stats can be monitored here: https://browsedns.net/topic/3917/dns-active-users-usage-statistics