Working from home reduces visibility, you don't work from home to make more and get promoted, you work from home to avoid the retardation of a commute, busy work, excessive meetings, etc. You work from home so you can put in 2 hours work, accomplish as much as anyone else did and spend the remaining 6 enjoying your life. I'm pretty sure that everyone who decides to work from home did so for quality of life reasons ra…
It takes me an 1 1/2 hours to commute into work. By that time, I'm exhausted from dealing with traffic. Next, you have to deal with coworkers and their noise noise noise. Everyone wants to small chat at my job. That's fine, but don't hang around my desk and try to get my attention while I'm staring down a bug (death stare). Its rude and I can't concentrate.
As a software engineer, I try to avoid as many meetings as possible. I just want to build the things that are needed to be built. Avoiding meetings helps with that for two reasons... 1) You have more time to work on a task 2) You don't have to break your thought pattern to fixing a bug/solving a problem
As you said, with telecommuting you get more done with less time. Its basically a daily mini hack-a-thon in your living room/Starbucks. I normally get in about 2-5 hours of solid developing. It really depends on the task and when I can review the changes to my boss for the final push. The rest of the time I can relax and think out the problems.
At work, I just can't concentrate that well. You're stuck at one location for 8 hours. At the same time, you just want to go home. With telecommuting, I can wake up later (which makes me more alert), work for a few hours, relax, and come back to the problem when I have those occasional "eureka!" moments.
Now, I like to say that working at home is the be all end all. I still need to show up to push code to production. I still occasionally need to talk to staff about what projects should be next on the list. But, if your main job requires you to just be imaginative and churn out code, then being isolated is where its at.