David looks amazing and I believe the overall online reaction is a positive. Also, have to laugh, the trunks and David's gifts behind the trunks are getting a lot of buzz as well. Both Superman and Lois look cute together, with little background information to add.
As for Cavill. This is Hollywood, many actors and actresses have been bitten by the system, in that he is not special. The main reason he was probably cast aside was that he is a mediocre actor. He may have his adherents, but overall the general audience was not impressed. Also Gunn likes a happy, working set. Cavill seems to have a reputation for not being that kind of actor, some even say he is toxic, especially to female writers. I for one wish him no harm, but I am glad he is gone.