I have worked with IBM MQ for three to four years.
The stability and performance are good and our customers are happy with these aspects. In my years working with it I haven't seen many issues, and with the type of support IBM provides, it has been fine.
I have been in contact with IBM support many times. I am satisfied with the support.
The initial setup is straightforward. It's not very complex.
Most of our customers are quite happy with the solution but they have an issue with the cost. They want to move to cheaper solutions.
The best advice I can give is that it provides stability and performance and there's no loss of data. That is most important for our customers. The data will never be lost.
It is used by large enterprises.