(written by lawrence, however indented passages are often quotes)
For Unix, the point of modularity was reached early in the 1990′s and, through the Linux implementation, it allowed the lowest layers of the software to become commoditized (and free). This commodity status was actually what Microsoft tried to avoid by integrating Windows with the layers above it. This was a conscious and deliberate decision which also led to trouble with anti-trust regulators. The decision seemed to have paid off. Microsoft won.
However, the very strategy which Microsoft used to maintain a monopoly caused its rigidity of response to a new, post-PC market. Unix fit right in with the new shift in the basis of competition: toward more personal, portable and conformable computing. Windows did not. Microsoft had to build a completely new OS to deal with devices (Windows CE has little if any shared code with Windows NT et. al.). The dual OS strategy continues to hobble Microsoft as each is stretched into new dimensions: the desktop Windows being dragged into the high end and into tablets while the device Windows is re-written to accommodate new input methods.
The modular Unix just keeps conforming to new applications. It helps that it’s open source but the open sourcing is a result of the modularity not the cause for it. So far, it looks like there is no stopping the revenge of Unix. It’s been a long journey for Unix and I, for one, am cheering the comeback.