In all honesty I feel that the grid is another one of those typographic boundaries developed by the bold, systematic designers. I used to embrace the grid as a tool ( and don't get me wrong, it really is) but now I feel more to the notion that it inhibits my personal creativity. For example, our most recent project, in trying to develop a unique form of the common magazine I felt trapped by the restrictions of having a continuous grid forming the framework for the entire piece. Only until I abandoned the grid concept was I able to jump outside my comfort zone and develop my magazine in a direction that was truly unique to me. I have studied grid concepts and developed enough work based upon that grid toknow how it works and what it's purpose is. Come to find out, despite what most typographers, designers and such will tell you... I don't think it is entirely necessary 100% of the time.
In one form of design which I feel constantly requires a grid-like system is information design. Even if I don't love the grid idea, I love information design. I don't feel systamatized by the grid in information design simply because it is a more subjective form of design. It requires you, as the designer, to react as your audience would. It becomes necessary to organize information, not only to form a successful solution, but also because the message your audience recives is dependant upon how, and when they receive the information. Large quantities of text can bore the common reader, so being able ot organize your information can capitalize your design.
The grid to any designer is absolutely necessary. Once you are able to understand the purpose of the grid in both elemental and typographic form, you can then develop to be a better designer even without using a grid-system.