With the recent talks of fixing one of the most serious bugs with MultiRes (https://developer.blender.org/T58473), I think it would be important to advocate for an automatic Apply Base feature which will work as the default setting for the modifier.
The reason for this is that Apply Base as it currently stands is pretty inefficient for sculpting when it is very commonplace to go down to the lowest subdiv and be puzzled by how different your base model and final sculpt look like. As someone who has used ZBrush in the past, it has always made sense that sculpting on a mesh will affect the base mesh. Plus, I have found Apply Base to be overall pretty slow, and the time it takes to use it could be better used just sculpting away since I already know that I will have to use Apply Base sooner or later. Also, because of the previously mentioned bug, it very often causes nearly irreparable damage to your sculpt on the higher subdivs, so I have had my fair share of headaches using MultiRes.
While I personally don’t see much of a point in keeping Apply Base as a feature, I will concede that it can be left as an option for people who want to work as non-destructively as possible. Apparently Brecht said that it is possible to have both the destructive and non-destructive approach, so I trust him on his word about this matter. However, I will not concede on the point that the automatic approach has to be the default setting, since this is how it works in other programs, and so far I have not met one person who uses those programs who thinks this system is wrong.
