Depends if you're prepared to be collaborative on your tree or not. It's built around the concept of one single contestable tree, rather than a collection of individual (and often unsourced) trees. It has been primarily US-based but I think users from across the globe are expanding.
I've been using Wikitree for my online work and have made some great (Australian) connections. I personally find the concept of one single tree rather interesting. I monitor my profiles and haven't found anyone messing with them without a good reason and explanation (eg adding an individual to a particular category).
Most people I've come across on Wikitree are helpful and wish to collaborate. There is capacity for someone to (deliberately or accidentally) obstruct, but Wikitree has some work arounds for unresponsive or nonactive profile managers.
The main problem I find with Ancestry or other paid subscription sites is that you might find something interesting on a private tree, but you can't communicate with the tree owner unless you are also a paid subscriber. And then there are cases where the tree owner is no longer active, so a tree even with errors becomes 'set in stone'. The paid sites are great sources but have their limitations.
In terms of sharing information that you've spent money on. My Mother takes the view we shouldn't do it. But for me, as all genealogists would be acutely aware of, time travels and we'll all end up in a grave one day; what's the point of take all that research with you? If I can help someone else, or reduce errors, by sharing that GRO certificate, why not!
