- download the binary plugin,
- ensure that it's named "org.eclipse.ui.recentfiles_1.0.0.jar" (I've seen the name get munged by the browser before),
- put it in your eclipse/plugins directory, and
- restart eclipse with -clean.
I use it on a day-to-day basis (currently on Eclipse 3.3 M5, but moving to M6 any moment now). It's particularly useful when you've just closed all your editor tabs (Ctrl+Shift+W) but then want to go back to a file you just had open.
It works well when your working set of files is smallish. If it grows beyond 15, then Open Type (Ctrl+Shift+T) is still your friend.
Note that the Workbench already maintained this list of recently used files. It's the same as shown in the File menu, though the File menu only shows 4 by default. This can be bumped up via the "Size of recently opened files list" entry under Window > Preferences > General > Editors. But I find the convenient Ctrl+E binding, the central location of the pop-up, and the type-ahead filtering make the chooser much more usable.
If you try it, let me know what you think, either here or in the bug report.