Open your minds and get ready to grow.
The August, 2006 issue of MSDN Magazine shows you how. An excellent article for whetting your apetite that discusses the ins and outs, and the +'s and -'s:
Historically, developers have not considered Office applications as real development platforms because of tools like Visual Studio and ASP.NET. But Office is developing into a solutions framework and consequently a developers platform. This really began with Office 2003 but is really becoming mature in Office 2007. What does this mean? Well instead of just of suite of discrete client-side applications like Word, Excel, etc., Office 2007 provides a complete set of client-side and server-side technologies that together provide end-to-end solutions. So these are not just "point" solutions but also "platform" solutions. Office 2007 integrates client-side applications with server-side applications like SharePoint, Exchange, Content Management Server, Excel Server, InfoPath Server, etc. This is an extremely rich platform. From a technology POV, this brings together the the Office system, Visual Studio and the .NET framework. Therefore, developers have an already familiar, very rich, extensible client that will provide an excellent starting point for application development. The Office system now relies very heavily on SharePoint technology to provide a collaboration solution platform.
This article discusses one of the key aspects of the new SharePoint system....complete integration with ASP.NET v2. So, SharePoint Server 2007, aka MOSS, is now a true application platform on top of the Windows SharePoint Services v3 technology platform. This means that WSS and MOSS can easily be extended using ASP.NET v2 technology.
MSDN's July issue also cover's the customization capability of WSS v3 in the article:
Obviously, there is a lot of stuff here. So get some coffee and dig in.