It isn't soft wood underneath. It's Baltic Birch plywood.
The polyurea bedliner coating itself also has significant structural rigidity, and will stay adhered with small dents - although in 8 years of riding around crammed in with drum kits, mic stands, etc. banging into it - I haven't gotten a dent yet.
I've had cabs with pretty much every covering class - carpet, Tolex, Duratex, and Line-X, and by far the Line-X was my favorite.
The only two downsides are that it's relatively heavy, and if your cab gets into a fight with a wall, door, or your car... your cab will win, and win in a way that will make whatever you dinged pay.
Duratex is easy to touch up, which is its saving grace, but I still very much prefer the Line-X liner.