Yes, I thought SKU was compressed (zipped) COLLADA format. I thought that you could rename the file as .zip and then unpack it to a collada file. I think all 3D software is hard to use because the job is complex but I think Blender used to have a difficult UI to it. I am told that its been changed and improved no end since I last used it. Sketchup was supposed to be good for architectural modelling and something like Z-Brush and Rhino was good for curvy stuff. I also prefer OBJ format since its text based and pretty universal but it lacks a lot of specific support for the app which created the model so maybe another format like COLLADA would be better.