However, I am not interested (for now) in anything 3D. Is LWJGL too complex to learn just for 2D applications? How much work does it take to lay the foundation of a game in LWJGL vs. regular old Java? Should I just stick with the comfortable, familiar, Java 2D?
I managed to pick up the basics in a week, and created a foundation of a game using this code in about two weeks. I think it's well worth trying, and not harder than any other drawing API.
In this thread you can follow a bit of the story (from second half of the top posting):http://www.java-gaming.org/topics/learning-opengl-lwjgl/27785/view.html
Although this is more like 3D, I actually started with 2D OpenGl example which just drew a flat square. And other than the lansdscape all the objects are billboard, so actually 2D, too.