A website without I could not possibly be productive.
Its success tells a lot about the huge amount of tiny and fragmented knowledge is necessary to have when working in the information technology. As an average multilanguage developer / sysadmin, I'm impressed by the amount of new knowledge I need to acquire every month to get forward with my work.
Results from Stack Overflow often get in the way sooner than official documentation. For example I had investigated a warning when installing a DNS client, the answer on S.O. allowed me to understand that it was actually an error. When I prefer to see directly the documentation I avoid copy-pasting full errors.
I use the official documentation when answers on S.O. seem to be too "magic" to be blindly trusted or when I need a wider view over a topic.
For many uses, I wrote my personal S.O-like "reference". I couldn't find a way to get them closer to me than this (maybe print a cheatsheet and hang it to the wall?).
At the beginning of my career, I distinctly remember the spike in productivity when I've learned how to use a search engine (at that time only google). Today the difference is made by Stack Overflow.
Any amount of donation one can send to the website is not enough to really give back to the community that make it possible.
Let's hope that they won't become victim of their own success: many successful and appreciated tools made some wrong decisions and alienated the userbase.
Software developers are aften very picky on themes like advertisement, monetization, personal data usage and too many frills on a tool they're using for work.