Thanks for the feedback. We try our best to deliver all of our features for all supported version of Visual Studio. This is actually the first and only feature supported only in Visual Studio 2010. The reason we chose to go this way is that the new extensibility model that VS 2010 allowed us to implement it much quicker. Also the number of people using the new Visual Studio is quite large and continues to grow.
It is true that there are free VS extensions that expose similar functionality. However, we believe that our Structural Highlighting functionality is richer and allows you better configuration abilities.
the Telerik team