It might be impossible to find every bug, but surely you can at least make error messages more informative. Also, I am not necessarily talking about bugs. IMHO there is a problem with the underlying algorithms as well....
I am afraid other 85% simply don't get reported. Ask your users how many of the fatal or portability errors that they experienced they have actually reported?
In my experience until the device is approximately 50% full the tools work more or less OK. If they crash I can usually pretty quickly find a different combiantion of options, which will make the design pass. However, as the device gets more and more full the issues with the tools become increasingly more difficult to deal with. I guess in part it is simply a function of the compile time. But in part it is definitely the tools behave less predictable.
I think I won't be the first to say postpone any GUI work, any work on new features and concentrate on giving us truly robust and efficient back-end tools.
/Mikhail