For me, and I think anyone with a sensibly laid out system, it's so much less trouble and time to reinstall. I can only really think of one reason to dist-upgrade, and that's if the system is remote (and a very good reason it is). I'm wondering why some of you dist-upgrade ... do you just like it that way? A habit?
I keep my /home and my data (/share) and /var on a separate disk and only the system goes on / (an ssd). Still have to painfully deal with outdated configuration wrt the desktop environments, so I just make a new (fake) user to see what the new layout is.
The cons are that firstly, it's very time consuming and much more complicated. Second, and perhaps most importantly, you're going to be left with older versions of things when a paradigm has changed. I dist-upgraded for the longest time and was hence completely unaware of grub2 for several years, since the maintainers of it wisely did not upgrade me to it! I can see the same happening with init systems being switched about. I guess if you care and read the release notes carefully this won't happen though. But Debian was so reliable (I found) that it was pretty much a fire and forget operation with each stable release.
What's your reason?