Trying decide, apropos that famous Feynman quote, whether there is a 'real problem' with quantum physics. My own rather inexpert view is that if there is, the it's something to do with the classical limit. (The measurement problem being an interesting special case of this.) In particular because this is a substantive and indeed experimental problem. Although you wouldn't normally think that when I pick up a tennis ball and throw it across the room that this constitutes experimental refutation of quantum mechanics, I think that unless the phenomena has been adequately explained within the framework of quantum physics then that is just what it is. There might be such an explanation of course I just don't know what it is. On the face of it though it must be quite challenging reconciling such different descriptions of the world. Although on the other hand I suppose this is not so strange, we're familiar with the idea that the system can be explained by different laws depending on what the observables are, e.g thermodynamics is the appropriate theory if the observable is temperature and pressure and so on. This is sometimes called "emergence" although that may refer to something more specific. Anyway in the instance of me throwing a tennis ball I suppose the relevant observable is something like the center of mass motion and we some explanation for why such macroscopic observables like this obey classical physics. I'm also interested especially in comparing how Bohmian mechanics and the many worlds interpretation deal with this question. It's been argued that it's an important virtue of Bohm's theory that the classical limit question is straight-forward, since the classical position variables are in from the start and go all the way down so to speak. Whereas in the MWI, an otherwise quite similar interpretation, the quantum state comes all the way up. I have difficulty understanding how the quantum state of the whole universe gets sliced up in our perceptions into the classical world we observe. Any thoughts?