My TDAmeritrade account has also changed as of 12/20 and provides a link for "Info" in the Purchase Price column (and Gain($) and Gain(%) columns).
I have been checking for this since soundincrest posted about this on 11/26. No change was noted in my account on 11/26 and i have checked several times and taking snapshots of the My Positions page ... until I noticed it changed on 12/20.