I've been using Komodo Edit for the last few years, but am once again thinking of switching to Aptana Studio because of it's built in refactoring tools for Python.
One of the features I use all the time in Komodo Edit is "show unsaved changes". This simple feature pops up a window with a diff of the text in the current editor window vs. the saved file on disk.
There must be a way of doing this in Aptana Studio (or more to the point, there must be a way of doing this in Eclipse, since Aptana is built on top of it.)
How do I get a diff show unsaved changes?
Windows -> Preferences -> General -> Editors -> Quick Diff.
Check the 'Show Differences in overview ruler'. Set the combo on 'Version on disk'. Select nicer colors for the diff ;) and OK the dialog.
Now, every change in your file will be visible on the 'Overview Ruler' and on the 'Annotation Ruler' (the editor left and right bars). The marks will be visible until you save the file.
Not an exact match to the Komodo feature, but this, along with the local history feature of Eclipse, can provide a lot of control.
Hope that helps.