There are many possible approaches to the system init process. SysV init is certainly not the best solution. It has many advantages, including how simple it is (I have written many init scripts for my own use), but it is quite messy, and pretty slow.
I have used upstart a bit. This seems just as messy, not as simple, but the parallelisation does speed things up a fair whack. This is very welcome on a desktop machine.
I haven't used systemd yet, so I won't comment.
However, when it comes to a server, I want tried and tested solutions which are simple to administer. I don't care if it takes longer to boot up, because it will rarely be shut down. My home Debian server, running on desktop-class hardware, has been running continuously for nearly a year, and was only shut down then for a hardware upgrade. Business servers get shut down only when absolutely necessary. A change from 1min to 30s to boot up makes no difference in most server environments.
What Debian need to do is preserve the choice. Allow people to use systemd if they want, but leave SysV init available too. I know this is a more complicated way to do it, but systemd is not suitable for everyone, especially a lot of their core users.