As has been noted, the relaunch effect is a nuisance: if you do too much heavy stuff in the interim, DiscourseHub loses your place and starts out from scratch. And, of course, unlike a browser, there is no kind of tabs option, which would be immensely helpful at times.
For me, though, the biggest defect is the to-top scroll function (where touching the top of the screen scrolls to the top of the page). I use iCab for serious browsing, which does not have this at all relying instead on a persistent scroll bar (which can also be problematic at times). The problem is that the long-scroll pageless format used by Discourse means that scroll-to-top absolutely makes no sense. Discourse has its own little quick-scroll widget, anyway. The developer/maintainer needs to disable the scroll-to-top response.