Hi PaQ - the basic problem is that a very complex object that takes up a really big chunk of memory (like your objects in the file you sent me take up about 0.5 GB) can take some time to process.

For extrude, it is just taking that long to create the object and also the object's mesh.

Improving extrude will be a lot more difficult, because there is not an already existing equivalent object that can just be drawn in a new location like it is possible to do with transforms.

In the future to improve things like extrude it will pretty much require doing a kind of wireframe mode instead of shaded mode, a wireframe mode will avoid the mesh calculation step which will be the most time consuming part for something like extrude. But I also want to make the mesh calculation multi-core capable which should help out as well.

- Michael