That said, sometimes I use NetBeans (and sometimes I don't). I was using Eclipse for a few years, but I got so tired of the setup and wait. Of course, there is probably a newer, less sucky, version of Eclipse now, who knows.
NetBeans is fast enough on my netbook (Atom, 1.6 GHz w/ 1 GB RAM) for most little projects I tinker with (at least under Linux), and likewise on employer's workstation with real stuff (even using the mandated Windoze). The edit window is mostly responsive soon after start, though it may take a minute for rescan to finish so docs, jump-to-def and autocomplete to be available.
Also, I like that you can undock the edit window in Netbeans, putting it in its own relatively large stand-alone window. Throw in the "vi" plugin, and get to work, referencing the other window full of, um, crap, only when you really need it. I guess I shouldn't call the integrated debugger "crap", but much of the other stuff is :-)
I have some screen shots on my website of several file types, where I have undocked the editor and hierarchy widget. Playable for me, YMMV. http://roboprogs.com/devel/2009.09.html
Also, its easy enough to create a project with "external" (existing) sources, rather than the IDE-p0wned build process. I usually end up creating one (1) IDE project for a given source base, then checking out source for multiple branches and then either resetting a sym-link (*nix file systems) or renaming (MS-brain-death) the top level directory for the branch-of-the-day.
ido-mode + tags for navigating my source code, syntax highlighting + indentation for any language I do, pretty much nothing on the screen apart from my code, easy hooks for programming custom functionality
Everything I need from a code editor is the ability to open files in tabs, to syntax highlight any random language I use (on an average day I'll be using up to 5+ different languages) and to understand the indentation style for all the languages to ease indentation. Perhaps some bracket matching and that's pretty much it.
But what I seriously, seriously cannot live without is a HUGELY HUGE area for code. The biggest thing I hate in IDE's is that they tack on so many features and toolbars and crap that at the end I'm left with this tiny code editor that leaves me feeling horribly claustrophobic. Sure, I could close all those toolbars, but then why am I wasting resources on them in the first place?
Another thing I hate about IDE's is how egocentric they are. I don't like conforming to some IDE's idea of what my project structure should look like. And I certainly don't like it when they get horribly confused if I move a file through a normal interface instead of the IDE.
As for "keeping the project in my head" that some people mention as a problem when not using an IDE ... I've never found an IDE particularly helpful in that regard. I've actually never found any added value that an IDE would provide ...