One of the problems with using an IDE is that you're doubling your learning load, since you have to learn BOTH the language AND the IDE.
On the plus side, a good IDE can be quite helpful - for example, Eclipse tries to guess what you did wrong and suggests corrections. I especially like the "suggests" part - some have tried to simply forcibly fix the problem, leaving you worse off than before.
In the Java world, the worst IDE part is almost certainly using them to design visual components such as JSPs or
applets. Not only is the generated code usually pretty awful, I've yet to see any that did "pure" Java code - instead they use their own proprietary helper classes. Not what I'm looking for if I want to develop an open-source project!