Is there an advantage of taking my existing VBA projects and trying to enhance them with this Application?
Your better off writting the VBA code in VSTO .NET code.

Is there any specific benefits and/or disadvantages?
Benefits: Easier to write advanced code with only a few lines of code. Possible to to advanced features that VBA cant even touch.
Disadvantages: Only for Office 2003+. Price of VSTO.

Can I finally use my stylish forms????
Yes.