I would be surprised if any system administrator likes in-place upgrades. The simple truth is that they are not and can never be reliable. First you have to make the huge assumption that every software package initially installed on a system was packaged 100% correctly. This is never true. There are always packages with logic errors in them or that write to files they forget to mention in their package specfile. Writing package scripts is an incredibly unglamorous job, and is always assigned to the most junior developer on any software team.
Then, you have to assume that the host was correctly managed over time. Nobody ever went in and manually modified configuration or manually installed binaries that conflict with the packaged binaries. That never happens, right?
Remember that installing all these new packages means shutting down the old versions of the packages first. Package shutdown scripts are among the most poorly tested of all software. Nobody wants to deal with the incredibly boring and unthinkable case of their precious software package being deactivated and discarded. Plus there's a huge gotcha in this - shutting down packages which contain shared libraries means doing some very clever work to shut down packages which have those libraries loaded in to memory, or swapping running libraries in memory. That is extremely hard to get right.
Finally you have to assume that the people who produced the new release for the system thoroughly tested all possible combination of upgrades and not just the simplest case of upgrading the immediately previous version to this one. You have to believe that somehow they were able to devote the essentially infinite resources necessary to deal with every possible upgrade path.
As you can see, that is one giant (steaming) heap of assumptions. In practice none of those conditions are ever true. People install their own binaries on machines all the time. Package install and removal scripts are always buggy (I could write a whole dissertation on that one issue alone). The net result is that in-place upgrades are a fool's errand.
I should also note that my team performed a major OS and software upgrade of 7500 servers at my work last year. We tried so hard to make an in-place upgrade work but ultimately it just didn't, for many of the reasons listed above. We ended up wiping all the machines and installing the OS and all software from scratch. Problem solved.
All of this leads to my joke that the software release manager's mantra is Nuke it from orbit -- it's the only way to be sure. Completely wiping and reinstalling systems is the only sure path to success. You can get by with incremental upgrades most of the time, but eventually it's time to start fresh.