I personally noticed that the enthusiasm for Things plunged just after it was no longer free to use.
It may be that tagging actions is a great feature (I personally disagree with that view, but I recognize that others may think differently), but I think that the reasons that particular products seem to generate enthusiasm online are probably misleading.
Not sure if this is accurate, but since I switched to Mac I have found so much more of this . . . someone or a small teams makes a really good looking app with all kinds of potential and then it just stagnates and essentially dies. I get why it happens, creating something is fun. Taking it the final 25% with all stability and error free performance is where it becomes work. I recently have had this happen with a few apps . . . and it has forced me to start looking for more products that have a better chance of being around (with real updates) in a year or two.