"Extensibility" - The standard on this says "Consume Extensions" while the profesional says "All". What does it mean by "Extensibility" and what is the difference between "Consume Extensions" and "all"?
With Standard, you can install and use Visual Studio extensions that others have built. With Professional, you can build them yourself. For more information on Extensibility and what it means, see the following article: http://msdn.microsoft.com/vstudio/extend/vseoverview/