How to convert a web part project created in VS 2008 to VS 2010?
If I was starting from scratch, I would use the Visual Studio 2010 tools. But if you have an existing project using, say VseWSS, STSDev or WSPBuilder, I suggest you continue to use this. It should still work with Visual Studio 2010 after upgrading and possibly tweaking. I would not bother trying to restructure the solution to use the new deployment tooling in VS2010 unless there is some particular capability that is missing from your existing solution.