I've noted an uneven surface and wondered if this was just a viewer (resolution/compression) issue or likely to transfer to the printed model.
The wheel pan (the bit between hub and rim) should appear as a flat disc with a series of lightening holes but gives the appearnace of ripples across the surface - these don't appear in the modeller (Co|create) or the view I used to inspect the item (MiniMagic).
the model viewer gives everything the same smoothing group, so it will display flat surfaces with holes really weird.
Dont worry though, the printers will print it correctly since they cant do smoothing groups (obviously) so the flat planes will come out correct.
If you view the object in 3D, I think it gives a better rendering of what your printed part will look like (if it hasn't changed since I last viewed anything in 3D). The smoothed normals in the static view are just a shading trick and don't affect the geometry.