> As someone who really misses the flexibility of a flat file *and* IDE
navigation could you explain the benefits to me?

 As someone who works in Java/eclipse every day, I find scrolling through the flat-files hard on my eyes and a total mess.  The other thing that flat-file people seem to like are huge scrolling lists of packages, classes, methods, whatever.  Isn't it easier to simply type a few letters of what you want and make the computer show you a narrow list of choices?
 
 > Things I can't easily do now are:

>    - Look at more than one method at the same.
 
 Two browsers, side-by-side.
 
>    - Edit more than one method at the same time.
 
 Two browsers.  Navigation within a single "text file" is just different keystrokes/mouse movements than navigation between windows, right?
 
>    - Show how code is related by spatial relation to other code.
 
 Not sure what this means..
 
 >    - Move around a class in a fuzzy way, e.g. Page Up/Down, Ctrl+End in
Windows.
 
 I assume you want to page up through the source and method declarations.  I suppose you could file-out the class..
 
 >    - Look at class declaration stuff easily (is there or could there be
a key for this?). I'd just use Ctrl+Home in Windows to get to the top of
a Java file.
 
 Command+h on the class pane.
 
>    - Jump around the class method by method Ctrl+Shift+Down/Up in
Eclipse - Squeak might be able to do this?
 
 Sure, just arrow up/down the list of methods..
 
>    - Print out a class (though I haven't even tried this in Squeak)
 
 File it out and print it.

> With regard to showing how code is related, has anyone looked into
multiple categories for methods? Less about saying what a method does
but more about what methods it's related to (so maybe not a category at
all).

VisualAge does this.  Its more complex and I don't think it added much value.