In the startup world, I often hear very anti-office-space sentiment (either "don't get it" or "learn to rough it / cheaper is better"). I think this may be the after effects of the bubble, but that's an entirely different topic. Instead, I'll provide a slightly different perspective.
When deciding whether or not to buy office space (and how much to spend), I converted rent dollars to productive hours. For the sake of simplicity, let's assume that you are a one-person startup (as I was), and that you could easily get contracting gigs for $100/hr. Heck, let's be more conservative and consider $75/hr. Again, for the sake of simplicity, let's assume that your time spent on the startup is equally valuable as your time would be spent consulting.
In Michigan, a nice office costs around $400/mo. So, in order for this office to pay itself off, it must help me produce an extra ~5.5hr/mo of billable work (i.e. productivity). This amounts to around 11 extra minutes of productivity per day. This doesn't take into account other things like mental outlook, well-being, company attitude, etc.
So, in my scenario, I decided 2 years ago that yes, an office would add 11 extra minutes of productivity to my day. This is a decision each person must consider, as it's not one-solution-fits-all. And for a startup team, you must take into account everyone's individual productivity in addition to group productivity.
In my experience, I love having an awesome office and it's helped me through the day many times. However, I'm also constantly (and at time, painfully) aware of the cost of this luxury. For example, I still do more consulting than I'd probably prefer.