Back when I played.. I have to admit... it works best with no terrain.
Anything 3D, as mentioned, gets in the way of movement trays.
Archers have their use, but with buildings and trees in the way, they become useless for the most part (heavier stuff like crossbowmen and gunners become less useless, they have killing potential in a single volley...)

All in all, the previous edition (when I still played) looked like it was designed with a flat open table in mind, not with terrain of any sort.