In my personal experience, Soap UI NG Pro added a lot of value to our product. We have been able to automatize a lot of manual work in a really easy way.
I was given the task to search for a tool to implement the automation for the first time in the project, so, I've been testing many tools. However, the main features that convinced the client in the demo to choose Soap UI NG Pro was the possibility to run in such a fast way too many test cases simultaneously, SQL injection, and being able to save the tests as a WAR file.
It save us a lot of time that before was wasted in manual testing. For example, we used to test OData Protocol queries, so we needed to compare the XML in the HTTP response with the data retrieved in the database. As it was a lot of information, each tester needed to pay attention to all this data in both places. With Soap UI NG Pro, this comparison just took a few seconds. That was really amazing.
I have not been able to use this tool a lot of time, so I don't consider myself in a position to say what can really be improved. However, I would like to see some IDE plugins for Soap UI NG Pro. I don't know if you have it already implemented but, for example, an Eclipse Plugin would be great.
I would say that if you are in any doubt, they can really count on the customer support team, they answer really fast and their answers are really helpful. Sometimes, they can guide you through documentation that you wouldn't reach for yourself and all the information they passed me, at least, it was updated, complete and easy to understand. So, this is really helpful when it comes to implement a new tool.