This thread’s summed up just about every point of view, but I may as well add my thoughts too.
I love mine, an Arkose with WTB Horizon’s.
Feels as fast as I need on the roads, really quick actually. Yes, it’s boring on flat smooth roads, but that’s mostly as (I find) flat smooth roads are boring…
Off road, it gets quickly out of its depth on proper MTB trails. I can still make it through them often, but it may not be fun. But that’s what my MTB is for.
On easier trails though, fireroads and smoothish double track, it’s great. And the key thing for me is not just that it can do these, but it makes easy trails more fun than they would be if I were over-biked on an MTB.
The answer all depends upon where your priorities are and/or what your local trails are like.