You can see in the comments section of this article the deep feelings on designers’ parts about Theory Vs. Practice. If you take a look at the feature section of Gamasutra or read up on back issues of Game Developer you’ll see that there’s a lot of theory and very little practice. Most people try to give examples when writing articles, but very few people have written articles like “Balancing Starcraft” or “Level Design in Open World Games” or “How We Designed Grand Theft Auto”. Very few people talk about what they do at work every day or how they actually came to make their design decisions, which I feel is very unfortunate given that there are tons of people like me (and experienced designers for that matter) hanging on to their every word. I’m guilty of this too, of course, given that I haven’t released anything yet. But I try to give practical examples or point out design flaws in real-world games.
Some of the best articles are practical how-tos, some of which are useful even for non-programmers: http://www.gamasutra.com/view/feature/3725/measuring_responsiveness_in_video_.php