Visual Studio .NET 2005 includes many new features and enhancements compared to Visual Studio .NET 2003 for both Windows and web development. Key IDE improvements in VS 2005 include refactoring support, code snippets, enhanced debugging tools, and improved deployment options like ClickOnce. ASP.NET features were expanded with new data and navigation controls, master pages, and themes/skins. C# and VB.NET saw new capabilities like generics, partial types, and nullable types.