While I don't intend to have a LOT of verts/polys in my game - I'm told that the Unity terrain alone on IOS can slow things down considerably. No need for high-poly detailed models - and more so, not sure I need photo-realistic terrain or trees. I ran into the same issue with DemolitionFX years ago. I started out with it feeling like a more hardcore simulation - that didn't seem like that much fun. It took my young son, Ben to point out that "everybody likes monkey's with hammers!". So I will be ultimately switching to more of a toon-shaded (cel shaded) look and feel.
I'm enamored by some of the low-poly vehicles I find on SketchUp that I believe I can import (via Blender and then Unity. I am hoping that at some point I can develop the skills to articulate these things (even if I just break them up into a few separate objects and control them with Unity scripting).