In case anyone is interested I spent some time yesterday playing with this and in a word - Very heavy.
Okay two words. But it's about what I expected - Inventor is not the right application.
Now you have found it.
I don't think the Piping Package in Inventor is good.
Useless - this is my word.
It seems that Autodesk dumps it to Inventor for making money without providing users the effective tools.
It is not the right application, surely.
BTW, Add-ons from the markets for AutoCAD are always better than the one shipped with AutoCAD.