The language has been improved, the Framework has been improved and the IDE has been improved. With VB 2008, .NET 3.0/3.5 and VS 2008 you've got LINQ, anonymous methods, WPF, etc., etc. Basically, there's no reason NOT to upgrade EXCEPT that projects created in VS 2008 cannot be opened in VS 2005, including those targeting .NET 2.0. If you still need to open your projects, either yourself or by others, in VS 2005 then stick with VS 2005. Otherwise you should upgrade. Note that installing VS 2008 doesn't mean you have to uninstall VS 2005. They were designed to coexist and will do so happily.