More consultants, less employees?

I’ve had really good luck with hiring a few good independent consultants to get done jobs typically done by a full-time employee.

On the surface, this seems more expensive than the employees, but if I were to add to an in a reasonable 20% overheard for benefits and company contribution to 401(K) and stock options, it becomes quite comparable.

These consultants, who often do a lot of work from home, seem to be able to get done in 20-25 hours what a full-time employee is able to accomplish in a full 40+ hour week.

What have your experiences been with independent consultants? How are you getting your HR/CEOs to allow to move budget FROM headcount to a consulting line item?