Opinium has replaced the questions asking respondents whether they approve of the job being done by David Cameron as PM, Jeremy Corbyn as opposition leader and Tim Farron as Lib/Dem leader etc by equivalent questions which ask for each party leader whether the voters in the sample have a favourable or unfavourable view of the leader concerned.
Mike Smithson of "Political Betting" thinks this is a better question. Adam Drummond of Opinium explains why it was adopted. Lest there be any doubt, "he" in the tweet below refers to Jeremy Corbyn, not David Cameron ...
@MSmithsonPB mainly to counter the fact that all my Tory-supporting colleagues strongly approve of the job he's doing— Adam Drummond (@AGKD123) December 20, 2015