I was raised keeping the Sabbath fairly strictly, but not to the level of Orthodox Judaism. There were the things I "couldn't do" on the Sabbath that I really would have liked to do, but I always kept the Sabbath faithfully as a child. It seemed like a limiting restriction, but I did it anyway. After I graduated and entered the workforce, I started to appreciate the Sabbath more--probably for the same reasons that many commenters here recognize some of the positive aspects of the idea. It's a nice break from the normal routine, a chance to rest, rejuvenate, etc.

But now I do not keep the Sabbath any more. Somewhere along the line I rejected enough of religion that I didn't feel it was necessary even though I recognize the positive aspects of it. Now I work on Sabbath sometimes. I do side programming projects on Sabbath sometimes. I rest on Sabbath sometimes. Sometimes I rest, relax, and rejuvenate all weekend. I don't feel its necessary to take good guiding principles and observe them as strictly as Sabbath keepers seem wont to do.

But maybe that's just because of my personality. Maybe there are people who need a strict Sabbath to prevent themselves from overwork and burnout. I have a pretty high level of intrinsic motivation and drive myself harder than many, but I have a good internal burnout avoidance mechanism. I'm sure there are people out there who don't have that and for whom a device like the Sabbath might be very important. At the end of the day, I think there are very few absolutes, and I find that my life is happier when I'm not worrying about the Sabbath.