Michal,
We've used Dietrich's for two years now and find it to be a great program. I can quickly (<1hr) draw a conceptual frame for a potential client. This gives them a picture to look at, along with generating for me a timber list, panel wall heights, etc. etc. that allows me to provide an accurate and quick estimate. It is very easy to transfer 3D frames to 2D drawings. We don't use too many single beam details in our shop any more (usually just dimensioned bent and wall drawings), but they are fairly quick and easy to develop. It interfaces well with AutoCAD, which allows our designer to develop floor and foundation plans off of the Dietrich's program.
Justin Bush