In the fast-paced business world where every minute counts, the importance of an effective Productivity Management Software (PMS) cannot be overemphasized. The paradigm shift from traditional manual methods to automated operations has not only revolutionized business processes, but also necessitated the understanding of these tools before their implementation. Looking back in retrospection, there are a few crucial insights that I wish I had grasped about PMS before embarking on the journey of implementation.

Firstly, PMS is not an antidote to all productivity woes. It is an essential tool, certainly, that aids in tracking, coordinating and managing tasks and employees effectively, but it is not a panacea. The efficacy of a PMS depends heavily on the business model and the team's receptivity to technology. The Pareto Principle, commonly known as the 80/20 rule, holds true in this case. The PMS could help manage 80% of routine tasks, but the remaining 20% of strategic tasks may still necessitate human intervention.

Secondly, the most feature-rich PMS is not necessarily the best for all businesses. This is the concept of 'feature-bloat' or 'software bloat'. A system with unnecessary features, that are not relevant to your business operations, can actually hinder productivity rather than enhancing it. Hence, it is not about getting a software that does everything; it’s about getting one that does exactly what your business needs.

Thirdly, the adoption of any PMS is a change management process and should be treated as such. As per the diffusion of innovations theory by Everett Rogers, technology adoption is a socio-behavioral process. The transformation it brings, though beneficial in the long run, may be met with resistance initially. This transition should be managed effectively to ensure the team’s acceptance and optimal use of the software.

Fourthly, proper training and support are essential for the successful implementation of PMS. Even with a user-friendly interface and intuitive features, the lack of understanding of the system’s full capabilities could lead to its underutilization. As per the Dunning-Kruger effect, the users’ perceived competence in using the software may be disproportionately high in the initial stages, leading to overconfidence and mistakes. Therefore, continuous training and support are crucial.

Finally, data security should be a paramount consideration when choosing a PMS. It's not just a matter of compliance with laws like GDPR, but also about maintaining the trust of employees and customers. As per the economic concept of 'negative externality', a data breach could have far-reaching effects beyond the immediate business, impacting stakeholders and even the industry reputation.

Reflecting on the above insights, it becomes evident that the choice and implementation of a PMS is not a decision to be taken lightly. It requires a deep understanding of the business, its processes, its people, and moreover, the software’s relevance and effectiveness in enhancing productivity. With hindsight, had I known these aspects, the journey of implementing a PMS would have been smoother and more rewarding.

In conclusion, the quest for the Holy Grail of productivity is not about simply acquiring a PMS. It’s about making a thoughtful choice, facilitating a smooth transition, ensuring effective use, and maintaining the highest data security standards. As businesses continue to evolve and grow, the role of PMS, no doubt, becomes increasingly critical. However, understanding these essential aspects of PMS can go a long way in ensuring its success.