I'm a financial modeller, I skipped to excel 2007 a couple of years ago.
Not sure I fully understand your question, it took a couple of weeks to get used to the layout, tabs concept, new shortcuts, more powerful formula, etc...
but I don't think anyone will shut a door in your face if you haven't moved on from excel-2005... Modelling is always more about solid building, flexbility of variables, mental approach, financial rigour etc.
I didn't like it at the beginning, now I couldn't go back to older versions...still full of annoying little things though!
hope that helps