The tabs are all updated in real time, so that you can close a document by closing its thumbnail, etc. However, this feature is disabled by default, since if you have many open documents, navigating through the thumbnails becomes a hassle:
The technology behind it
SevenBeans uses J7Goodies - a Java library that provides all Windows 7 features in a developer friendly way. This is a very good product, I put a lot of effort into it so developers using J7Goodies can integrate Windows 7 functionality with their application in just a few lines of code.
Having the J7Goodies library, I was looking for a way to showcase its abilities and I wanted it to be a real world example. Because I'm using NetBeans, which is a great IDE and even greater rich-client platform, I came up with the idea that I could improve the NetBeans experience on Windows 7 and showcase my library at the same time. I believe that it was a good idea because SevenBeans user base is growing at an incredibly fast pace and it is getting a very good feedback.