Recently I been spending quite a bit of time on a forum that is running different forum software… and I found it to be quite irritating!
- Having to scroll all the way back up to the top to go elsewhere
- Having to scroll all the way back up to the top to check the next notification
- Notifications not being marked as read when you visit the topic of notification
- Slow/sluggish speed
As you know DC doesn’t suffer with the above and generally, it’s just a much nicer experience being on a DC forum than it is on one of its competitors. So well done the DC Team, I know I’ve said it before but no harm repeating myself 
The only thing that’s lacking (or preventing me switching some of my other forums) is easa-of-porting from other platforms (import scripts), and being able to customise to the same extent as other platforms (though I appreciate not many people customise to that extent, i.e. to power other sections of a site).