Given the popularity and ease of use of Visual Basic 6, it's little surprise that Microsoft makes it easy to build applications that use both Visual Basic 6 and Visual Basic .NET. Developers can write applications in VB .NET and bring legacy Visual Basic objects into the new app, or they can leave existing apps in VB 6 and call into the .NET Framework to take advantage of functionality not native to VB 6.
One concern that arises with these so-called "hybrid" applications is maintaining them.
A recent MSDN article by Scott Swigart addresses hybrid application debugging. It covers both VB .NET apps that use VB 6 components and VB 6 applications that use VB.NET components. As expected, both processes require a bit of switching between VB 6 and Visual Studio 2005 -- but it's a small price to pay for a bug-free application that offers the best of Visual Basic 6 and Visual Basic .NET.