What do you mean by "crazy distortons in the geometry"? Do you mean actual distortion or just shading anomalies?

A well-made sketchup model will import into poser just fine. Sketchup's biggest strength is also its biggest problem: SketchUp is so easy to use that you don't need to know anything about modelling, anyone who can click a mouse can start modelling something that looks ok on screen. It is also extremely forgiving of sloppy geometry. Unfortunately this means that a lot of the models out there were thrown together by clueless people.

Good luck finding a well-made sketchup model in 3D warehouse, the only ones I have come across there were pirated from pay-sites like Formfonts. The main thing to check for is inside-out surfaces, a lot of users just make both sides the same color so it "doesn't matter" which way the normals face - until you want to use the model in another application. Another common problem is internal polygons which divide the model into compartments, they cause headaches with smoothing and subdivision.