How do other folks find Blender’s built-in Collada importer? I tried it with a few files from the Trimble (née Google) 3D Warehouse, and found it too often did a poor job, particularly getting the placements and sizes of pieces wrong.
Then I found someone had written an entirely separate exporter and importer based on pycollada. It was a bit neglected, so I revived it here. It makes no use of the OpenCOLLADA code that is built into Blender.
I hacked it about a bit, adding custom extensions to represent some Blender-specific material settings and the like. I make no claims about its performance, and certainly it works in quite a different way. But it has done a much better job with those particular files that I was working with.