I worked alone from a home office for 20 years in my consulting practice until, in the last year, as my company has grown, I've moved to commercial office space for the first time. I found working at home a delight, and enjoyed many years of jokes about my short commute (18 feet.) However, in the end, I found the repeated advice of friends to be correct: I'm more productive with an outside office. The extra focus more than offsets the cost of rent. Being in commercial office space has also made it easier to meet with clients. It's also more social as there are other people at the office that I can talk to (or ignore) as needed.

My commute is still short (I often do it on a Segway), and our company is still virtual (with both staff and contractors working from their own spaces -- which we don't plan to change), but don't underestimate the value of a separate, outside, workspace.