I used to be able to see how many movies I had seen of other user lists what happened to that?

The little bar graph in the right column of a list page has been eliminated as of the Dec 6 update.

You can Refine the list: You and This List > Titles I Rated

Or you can alter the URL and get a condensed version of the list with that statistic and other options. Just change the word "list" in the url to the word "seen"; ex:
https://www.imdb.com/list/ls027794353/
becomes
https://www.imdb.com/seen/ls027794353/

For more on the Seen functionality:
https://getsatisfaction.com/imdb/topics/faq-imdb-seen-gets-an-upgrade