Ed Sim writes an entry called "When to hire a VP of sales":

Hiring a VP of Sales is not a commitment to hire one guy, it is a commitment to bring on a team, one that will not be cheap.  Before you make this commitment, make sure you are ready.  As you can read from an earlier post, when you ramp your sales efforts is critical.

Do more with less and be careful of ramping up sales until you have a repeatable selling model.  In other words do not hire too many sales people and send them on a wild goose chase until you have built the right product, honed the value proposition, identified a few target markets with pain, and can easily replicate the sales process and model from some of your customer wins.

Many of the best companies I have seen have taken the bootstrapped approach where the founders of the company act as the initial sales team to close a few deals, to learn about the customer, and further refine the product.  Yes, this can only last so long as everyday out of the office or with customers means another day not developing the product.  That being said, rather than hire a VP of Sales first, I would encourage you to focus on generating leads and hiring a sales rep or two to follow up on them.  This way you can take a smaller step to refine your sales model and product before going big.  Remember don't hire a VP of Sales to only have them hunting for dodo birds.

We're pretty confident of our software. Our next steps all involve selling it.