Well, this problem (if we may call it a problem) has been solved now by Blogger. You can have your post feed sorted by Published date, or by Updated date.
If you have the Recent Posts Widget installed to your Blog, there is a slight modification in the code you have to make. Edit the Page Element, and change the code like this:
Notice the orderby-parameter: there are 2 possible values: published and updated. Omitting the parameter is the same as updated.
The Recent Posts Widget Installer has been improved, and now supports the orderby-parameter.