For the past three years I've been teaching high school computer classes while using Java to teach the basics of programming in class. My usual routine is to teach HTML and CSS in the first semester, which provides the students with many of the basic skills of programming. Then in the second semester we start actually programming with Java.
The past two years I've taken advantage of the Greenfoot framework for Java. It eases the use of graphics and sound in Java programs, but more importantly it provides a visual representation of classes and objects. This greatly eases the burden of teaching what object oriented programming is all about, as well as demonstrating its advantages.
My reasons for using Java are several. Briefly, it's multi-platform. It's a "real" language, in that it is used outside the school and professionals are employed to use it. It incorporates the available facilities of the system, including graphics and sound, natively.
One of my hopes for my students is that after using Java in class, at least some of them will use it outside class as well. Unfortunately, for many of them the installation process has been a roadblock to doing this. Particularly in Windows, where an extra step has to be performed to add the Java SDK to the system's path. The students with Mac OS X at home are lucky, they don't have to install the SDK, it comes with the OS. The Linux users are usually capable of managing it for themselves. But about 80% of my students are under Windows outside of class. And the Java SDK install isn't what they're used to.
The installation barrier won't be the only thing my choice of language in class hinges on, but it's certainly a significant factor. Exactly why the Java SDK install has remained so hostile to Windows users is unclear to me. It smacks of elitism on the part of Sun/Oracle (if you can't hack the install process, we don't want you using it), but then the old saw about not ascribing evil intent where simple incompetence will suffice comes in. Maybe they just don't think it's a problem.