That'll be enough for the vast majority of forum users (on the personal side just wanting to have their own community) to steer clear of the software. I mean, it may be a decent forum to use but the thing is that they have the funding behind them to be able to invest into the software. Flarum is young and despite it being very active, people are worried about the beta tag that the software currently holds.
It will always come down to what you want out of the software you choose and whether it meets your needs and expectations, and in some cases the look and feel. There's not much else to it. One of my most successful communities was not using vBulletin, IP.Board, phpBB or even MyBB, it was a SMF forum. It had everything that I needed for the community and my members commented on how great the software really was. It was my biggest mistake that I decided to go to software that I thought was 'better' (IP.Board) and I lost the majority of my activity and members. Change isn't always good and if it works then continue using it; don't fix what ain't broke.
The only reason I ever change software now, or in this case swap to Flarum altogether, is because I am starting a new project. I am not migrating from anywhere and so far Flarum has everything I need in a need little package. I definitely see the potential in the software and I am confident that the developers will get a stable released and will continue maintaining it.