Acceptance criteria – NT network

I am an IT Manager within an NHS Trust. I am about to use a partner to take on the primary contractor role in a project to migrate our existing Novell network to Microsoft NT.

Traditionally, acceptance criteria have been based on meeting specific requirements but I feel this is a high risk method for anything other than a simple discrete project. I’d therefore like to develop acceptance criteria requiring that the delivered product is “fit for business use”.

What I don’t want is to endup having endless discussions, and possible disagreements, over the interpretation of fitness for business use so I’m looking for guidance from anyone who has relevant experience.