What I have seen on reviews is that this is not an ICS issue, but rather because the Galaxy Nexus doesn't include a SD card. Which can be a good thing.
The article you linked to explains that in the fourth paragraph. Their reasoning is that they don't want people to need a file manager in Android. It makes since to me.I like that they are going to a one large internal storage location.
It's neither really. The reason is that the data filesystem used to be FAT, so that it could easily be read by host computers using the preexisting USB Storage standard. But FAT sucks (for reasons too numerous to list here), so they went with ext4. But that can't be mounted on anything but a linux box, so they had to pick a new file exchange mechanism. It could have been something like SMB over a USB CDC network device (phones have done that in the past) but they picked MTP instead.
