Very difficult to sketch on a plane which is rotated away from the orthogonal grid. This is critical in architectural design. I can think of many modeling softwares that allow the creation of auxiliary work planes. In fact I have difficulty think of another that lacks this feature.
Why do you find it difficult?
If I have a planar surface that is rotated in respect to two axes I can place the work plane on that surface by double finger tapping but the am unable to rotate the grid around the normal to that plane. It occurs to me that if I create a new plane with zero offset I can rotate that. One more step. I think I get it. It would be nice to have a tutorial on just this subject. I have a related question about how to create a 2D drawing of a face of the model that is not aligned to the orthogonal grid. A rotated view plane in other words.