Honestly I have not. So the problem you have seems to be implementation (user interface) right? Rather than the actual dictionary it uses?
No, both MS has a very limited expansion unless you create a new dictionary for engineering terms then you have to keep switching back and for between dictionary's. see my comments under customization group
http://forums.autodesk.com/t5/Autodesk-Inventor-Customization/spell-checker/m-p/2699443#M32351
msk
