It's a good conceptual design tool. Quick and dirty. You can input dimensional information into it if you want better accuracy.
Plus there are tons of other sketchup models freely available to help you populate your model for added "realism". It's rendering engine is really simple but I like it that way. There's no mistaking that the model is a sketch and not a completed design. Gives you room to keep designing as opposed to locking in the design if it looks too polished and complete.
I have seen some architectural firms design high rise hotels, etc with it. Obviously they are not using the model for CDs.
used properly it's a really cool tool. If you expect too much from it, well then you can't help but be disappointed.