The barn where I board has two, and I've ridden both. One I rode for a while when I was between lease horses, and even took him to a show. It was a nice change, since every other horse I had shown up until then would get nervous at shows, but this guy couldn't have cared less. Very steady, though not ideally conformed for dressage, as his very thick throatlatch made it difficult for him to come in to the bit. He's normally used in a therapy program for disabled riders.
The other one is a little lighter build, and better suited for dressage. She's definitely more stubborn than the other one; when I rode her, she hadn't been ridden in a while, and it took a few rides to convince her to really listen to me. She was actually quite forward, with a nice, quick trot that felt like she could go all day. She belongs to my trainer, but is not one of the horses that she shows, so she sometimes doesn't get as much attention. I tried her on a trail ride once, and wasn't all that happy with her. She's plenty brave on the trail, and willing to go over anything, but she HATES being in the middle or back of the group. The time I rode her, she was behind about 5 other horses and worked herself into a lather trying to barge her way through. I don't particularly like trail riding horses that I have to be constantly hanging on their face. The horse in front of her ended up kicking her because she wouldn't stay out of his space, and I can't say I blame him (luckily no one was hurt)
Based off these two that I know, I think Fjords can be a bit dull sometimes and don't show a whole lot of personality. They are, however, solid and dependable mounts.
I was very excited when I was horse shopping to go see a Fjord x Morgan; I figured the steadiness of a Fjord with the overachieving personality of a Morgan would make a good combo. Unfortunately, the pony didn't get much of the bulky build of the Fjord and was a bit too small/narrow for what I was looking for. He was super cute though