We used vBulletin from 2001 to 2020 and still use it as a “read only” reference site (vB3.8.X).
Honestly, there is nothing I miss from vBulletin; and in fact after moving to vBulletin I found the MVC model of Ruby on Rails to be far superior to the LAMP model used by vBulletin (from a sys admin and web dev perspective).
From a user experience, most of our users are very happy with Discourse; however we did lose a few long established experts who loved the legacy / vintage look-and-feel of a vBulletin forum.
I had plans to port our legacy vB reference site to Rails in 2021; meaning I was going retool the site to a Rails, Redis, Sidekiq, MySQL, jQuery, Bootstrap reference site (build a Rails app on top of the existing MySQL DB); but I’m so busy with fun and interesting paid Rails client work in 2021 that I don’t think our legacy site will be retooled this year.
Before installing Discourse, I was an avid PHP programmer; but after migrating to Discourse and working with Ruby and Rails, I do not enjoy anything about PHP and LAMP web dev any more and am a big Rails fan thanks, in part, to migrating from vB to Discourse (and then learning Rails after years of PHP web dev).
Sorry to repeat myself, but as far as our vB site was concerned it was “good riddance” to vBulletin and their LAMP architecture; and “Thank You Discourse!” for building Discourse on top of Rails!
Hope this helps, @MKDan