I'm sure you know about this already, but didn't see a post. As of now the electrical panel schedule portion of building systems 3 is not usable in a situation where multiple drawings are used for a building. For instance, many times a panel exists on one floor of a building(one dwg) and a device exists on another floor(a different dwg) which is fed from the panel. There is no way for building systems 3 to keep track to these situations and therefore, this portion seems to be virtually useless(to my firm anyway).
Another interesting addition to Building Systems 3 were the Demand Factor styles. Well according to the NEC you can't just assign demand factors to anything you want. For instance lighting must always remain 1. Not a big deal, we would just always have our demand factors set to 1 for everything if we ever used this feature.
It seems this software is becoming more and more an engineering tool, to be used by engineers as they design. In larger firms I don't see this as practical. It has become increasingly difficult to get error free documents out the door, and in my opinion a great deal of the blame falls on the software. All these features built into the program would be great if you had a small building such as a house to design. However, for multiple drawing structures I think about all you can use is the ADD Device interface. Even this has become difficult to customize.
Sorry for the griping, let me know when you can handle multiple drawings, for now I just don't see it as usable and should not be advertised. There have been some huge steps made, but it is not there yet.