Its not just about the features, but you do need to know what you are selling​​

This is subtle one - its about the style of different pre-sales people in your team. I have seen both ends of the spectrum, where at one end you have the "techy" who knows the ins and outs of the product, but forgets to focus on value. And at the other end you have the pre-sales person that really wants to be a sales exec and skims over detail, often using force of personality to railroad their points across.

Both can harm sales cycles. The techies typically need coaching so they start putting their love of features into perspective and put themselves in their customer's shoes. The sales pre-sales people often need balancing (adding in a tech session to the engagement plan with a customer) or moving to the right role...

Ultimately a good pre-sales person knows enough detail to go at least one layer deeper than they are presenting/demoing/talking about, and it needs to be about the delivery of that product or service, not just the features of it. So in software terms its about aspects such as the implementation, support, security etc. I recall feedback from one potential client where they bemoaned the fact the previous team's pre-sales person took nearly all the questions away.