Ranked in these QuestionsQuestion Ranking
Pro Attractive pricing
It is possible to build production grade apps even with the free version. Pricing is decent when compared to competitors like Xamarin.
Pro Vibrant & helpful community
Pro Multi-platform development environments (via build server)
You can even use Linux desktops to build native iOS apps, no need for a Mac.
Pro Highly customizable
By utilizing lightweight component architecture and the built in graphical designer and theming options you are able to customize a good looking app on any platform.
Pro Works with all IDEs
Works with NetBeans, Eclipse, IntelliJ, etc.
Pro Java 8 support
Pro Open source
Pro High performance
Con Outdated Windows Phone port
The WP port is laging behind but that's on the short-term roadmap.