Use Jikes: http://oss.software.ibm.com/developerworks/opensource/jikes/
It's free, it's very fast and has much more friendly and easier to understand error messagess. Many IDEs can use it too.
Also, if your use Ant
as you build tool it can incrementally compile (among many other things) and it can use jikes.
If you're hoping to use something to build whatever you're working that has the custom classloaders I would recomend Ant. While using an IDE as a build tool can work it won't have the flexabiliity to setup and (re)package files like Ant.