Best way to program a word add-in

Hi experts,

I'm looking for a little bit of design advice.

I've been building a Word add-in with VBA and I like how that's been going.  At this point I want to start building this as a solution that can (one day) be deployed as a fully fledged Word add-in using either VB.NET or VB6.  However, I'm not sure which is more appropriate.

If I use VB6 there'll be no compatibility with Word 2007, there's less guidance from Microsoft and I'm fundamentally programming in a system that has been replaced.  However, the VBA code will require little adjustment, there's less to learn (all I know is VBA) and all I need to do is find an older version of Visual Studio.  

However, if I use (and learn) .NET, what is the implication of calling Word through the COM/PIAs?  Faster?  Slower?  More importantly, I'm using Visual Studio 2005 with Word 2002.  Does that mean my solution will only be compatible with 2002?Forgive me if the question is too unexpert... but on some of these basics there is very little support!

Thanks in advance for the assistance and for any advice you can offer on this.

Cheers,

PatternNut