I like working from home 1 or 2 days a week. I can take the dog for a walk over lunch, I don't have the commute (1 hour each way) and I have a much more comfortable working setup at home than in the company office. That I can't be interrupted is great, I'm not uncontactable as I'm on IRC but I choose when that happens rather than someone else deciding when.

More than that and I see diminishing returns, it's harder to bring structure to the working day and the communication thing is much too skewed in my favour.