I did not experience any trouble going from QV9 to QV10, but I did have one problem with going from QV8 to QV9 when opening one document. We were able to narrow the problem down to one expression within one chart. Once we changed the expression the document loaded as quickly as before. I would suggest you try to narrow done the problem.
The problem sometimes is in the data model intself so you might have to load only parts of your data model in order to find a table that is causing the QVW to be slow.
