Cars will always depreciate unless they are desirable cars in limited numbers. I think the I-drive debate is rubbish, old v new is minor. Mine is old, my brother has the new version and there is not that much difference. Go for what you can afford, 07, 09, 11, it all depends on what you can afford. The new model is still at least 2 years away but I don't feel it will impact the resale value on the V8 much as this series will become a true classic as they will be the last of the naturally aspirated versions!
