I've been using Syncfusion Essential Studio Enterprise since 2003 in all its versions as its evolved. Its moved from a purely a Windows Forms library to supporting ASP.NET, WPF and Silverlight plus a bunch of non-visual components such as DocIO and XlsIO. These are really useful as you can create and interact with Word/Excel documents without the version hassles and bloat of needing MS Office necessarily installed. This is particularly important for ASP.NET apps.. Its great having a one stop shop for a bunch of functionality that keeps recurring as a need in "Line of Business" development. Developing this level of functionality in component libraries is incredibly expensive. It just makes sense to source this level of functionality externally and Syncfusion provides a heap of the functionality in a nice neat bundle. The infrastructure that comes with the components is also extremely useful. There's an assembly manager and a build manager. It makes it easy to work with multiple .NET framework versions - removing and installing different versions as required. The libraries optionally come with source code. The beauty of their build manager is that you can easily choose a Component suite version, build in debug mode and install as the default assemblies. You can then flip back to the default release mode assemblies when needed. This level of control just makes it easier to develop and test with - and step it into their code if needed. Highly recommended.