Review: Is the 2015 Aventador a Worthwhile Upgrade?

I recently had the opportunity to get behind the wheel of a 2015 Aventador and I'm curious to know if it's worth upgrading from my current 2009 model. The new car has several upgrades including a more powerful engine and improved aerodynamics. But are they significant enough to justify the hefty price tag? Has anyone else made the switch or considered doing so, what were your experiences?