I've used JCreator a bit and have come to like it it has little neat features so when you type Math. a litle of all the available methods will pop up automatically, as well as the areguments needed (ie int, int), not only will those methods pop up but all other inheirted methods for when you use it on a variable. Another neat feature is that you can collapse/expand methods that you don't want to see or even comments
see this for a screenshot http://www.jcreator.com/screenshots.htm
the program I use now is a editplus http://editplus.com/
it supports many different languages and you can build your own custom tools into it
I have tools built in depending on whether I am working on Java 1.5.0, Java 1.4.2, Microsoft Visual C++, Metroworks C++, or PHP.
Neither JEdit nor JCreator are development kits :)
J2SDK 1.4.x are indeed probably the most widely used today, but I'd advise anyone taking up Java to start learning the 1.5 (5.0) from the outset as it is the future and by the time you're up to speed it will likely be prominent.
I really like JCreator and all of its features. I also tried blueJ and I really disliked it. Eclipse sounds good just because of the easy way to make layouts for applications... but the code is hard to modify if the program wrote it.