What do you like best?
The user interface is really easy to use, because it's so simplified. It includes everything you need to learn and focus just on the code. The errors and warning pane is useful and it's actually verbose, so you can understand what is quickly happening with your code. The debugger and stack view is very helpful, and I like the fact is also just the essentials you just need to learn.
What do you dislike?
It would be really nice if the user experience went under a proper review by an UX specialist, because in some cases the interface isn't intuitive enough, so you as an user have to explore and try "get the hang out of it" several times, specially with the debugger. That is not a problem after you get used to, but if you leave it long enough, you'll find yourself exploring again in order to use it effectively.
Recommendations to others considering the product
Learn to use the integrated debugger, it will help you in the long run to properly learn Java. Just because it's a simplified IDE doesn't mean you can't do advanced software with it, it's all in your hands to do useful code to suit your business needs, as long as you understand it's just a front end of the JVM. Of course, after you're skilled in Java, you might as well move into Jetbrains IntelliJ or the default Netbeans.
What business problems are you solving with the product? What benefits have you realized?
As a tool for introduction to Java Programming, it certainly does its job just fine. I value it's barebones, so you can focus on what's really important into your code.