>How do you measure 'progress' in projects written in O-O languages? 

If we can measure the progress of projects not involving software,
we should be able to do it for any software project.

Make a list of all the features that your project should support.
Make a list of the various deliverables, ESPECIALLY having the
feature running in the system, but including earlier design stages.
Make a schedule of all the deliverables.  

If a date comes, and you haven't delivered, you are off schedule.
As long as you keep producing deliverables, you are making progress.

Of course, some deliverables are better indicators than others.
In my experience, design documents are not nearly as good an indication
of progress as working and tested code.  You are better off if you can
build your system in lots of small increments, because then the only
measure you need is "system passes tests for feature X".  If you have
500 features, and it passes the tests for 250 of them, you are probably
half done.

For a more complete description of this (well, actually it is a complete
methodology, in which this is just a piece) see
http://c2.com/cgi/wiki?ExtremeProgramming

-Ralph