Ian that's a good question, I believe that if you let them do the talking then answer their question but indepth but it's like the long windered replies you can get you don't listen if it's too techy or boring.
Keep answers shortish but not too short, if you are asked a simple question say Yes or No to it then slightly enlarge upon it but not too much and then if it's an interesting topic to them they will ask more about it a bit like a cat and mouse feed them a line then pull them in then let it go etc.
If the customer feels as though they have done most of the talking they don't feel as though they have been sold to.
Shaun
PS selling is an art and when you have got a good 'script' you can keep using it but don't forget it will have to be kept modified as each customer has different needs and understands things in different ways.