If start-up time is an issue for you then you aren't using eclipse as an IDE. Eclipse and now IntelliJ is my primary development environment. IntelliJ is basically running on my machine all the time. IntelliJ may have an advantage of eclipse here in that it can have multiple workspaces open - I don't know if eclipse can do that.

I use SlickEdit for C++ and it starts much faster, but while it can "do" java, its completely ineffective compared to IntelliJ or even eclipse. OTOH IntelliJ occasionally hugs all 8 cpu threads trying to grok spring bean usage across three maven projects. Its a price I'm willing to pay.

And finally theres TextMate and Joe or on these knackered solaris boxes, vim. Can't really beat vim for start-up time, but unlike some of my genius friends, I can't get my head around it for large projects.

My point is, if your use case is open editor, open file, edit file, close file, close editor, then you don't want an IDE, and there are plenty of great editors for your use case.