After getting used to it, I quite like it. I really hope Redhat/Suse/Gentoo will also implement it, but I'm not expecting it.
Will Debian do the /usr merge?
Probably not, since it was not invented there. Just look at them sticking with .deb even though RPM is technically superior and recommended by LSB. Even the RPM version they recommend had to be neutered since .deb simply is not capable of all the features of RPM even after conversion using alien.
If they could let go of their NIH syndrome, this silly restriction to LSB RPM would be thrown away.
It's like Microsoft having created .exe and .msi as the de facto formats for Windows and suddenly some wise guy from another department says "hey I have a new packaging format .abc which should become the standard packaging and executable format for Windows and you have to use it as the new standard format because the Microsoft board said so." No way will the Windows department obey that order.
So which features does rpm have which deb does not?
I hope Debian doesn't do the /usr merge, and Debian policy appears to look strongly askance at it (starting after $local_fs, etc.)
The standard approach is to increase the number of supported scenarios, rather than decreasing them.
A *.deb package is an ar archive containing two tarballs. RPM is a varying binary format (currently around version 5, IIRC) which apparently has some relationship to cpio, but can only be read by custom tools.
Now, to install an RPM-based system, you need to start with a custom tool. To install a debian-based system, two archivers that are found on any unix-like system capable of building software are all you need to start...with the result that someone who knows what they are doing can install Debian Linux from a BSD system.
Reusing standard tools gives you a much more flexible system.
Delta downloads are an interesting feature...when everyone has access to the repository. LSB RPM is meant for those who ship proprietary software for multiple distros, which for quite some time meant shipping CDs with packages. At present, there isn't a universal package manager capable of handling repositories, let alone delta downloads; to establish this would likely require standardizing apt, yum, or zypper, or at least an archive format...which is likely to be a worse mess than dpkg vs rpm.