Check out the new article comparing the use of Data Matrix and QR Code in busy documents. Many people seem to be choosing Data Matrix because it is the current "popular" 2D symbology. But in time critical applications where decode time is an issue, QR Code and its more dense version Micro QR Code provide a significant performance advantage because of their good finder patterns.
Since we have no idea what we are going to write about, feel free to make requests. In the future, expect to read about our favorite bar codes (RSS, Telepen and UPC), the worst images we have seen, and whatever else we may be in the mood to write about.