I've gone back through 8 pages of thread titles and searched for 'multi' and can't find any mention that you can now search multi-city awards at co.com. So this is either a) really old news, b) buried in the massive co.com problem thread, or c) it's a new feature roll-out.
Granted (big surprise) it's a bit flakey, but a big step forward. For example, tried searching MCO-LIR, LIR-EWR (stopover), EWR-MCO and it wouldn't work - but MCO-LIR, LIR-EWR works fine. (So, technically, the feature can handle open jaws but not stopovers). Haven't played around with it much yet - wonder if you can break up and search/build trips segment by segment (minus stopovers) or if that would confuse the system too.
Now just have to call in to have the EWR-MCO flight added. to my reservation..