I wasn't aware that Horseman had a 617. But the 90mm is pretty standard on the Linhoff, Fuji and a few other makes. You also have the option of adding other lenses eg. 180mm, 300mm with their respective lense cones depending on the camera.
I have th Fuji GX617 which I bought with the 90mm. It's a nice format for landscapes with a good field of view. I've added a 180mm to my kit, just because I wanted a bit more reach for some locations where I'm unable to physically move closer. But so far, the 90mm does about 75% of my shots just fine.
If you've got a good link for the Horseman 617, please post it. I'd love to take a look at it as I already own 2 other Horsemans cameras (4x5 L Series and a 45FA).