I generally agree except for the install-time bit. My last job was as the technical director for a school division. We ran mostly Windows on user machines and mostly Linux on the back-end. I did a lot of installs of both Windows (XP & 7) and Linux (Ubuntu Server) over those years.
Getting XP or 7 to the point where one could image it onto a bunch of other machines took us at least a day. We didn't leverage AD as much as we could. If that were the case, it likely would have taken less time, but I'm not sure how much. Installing updates was, by far, the most time-consuming part. We tried to schedule that for the end of the day so the bulk of it would be done by morning. Next up was setting up the software suite, and then the virus scan and disk compaction. Finally, the little details about the desktop environment needed to be dialed in before imaging.
Setting up Ubuntu Server on a box took under an hour. Our procedure for setting up a file-server (which included several other services) could be executed in at most three hours. Heck, on Friday, I upgraded an Ubuntu desktop box (with a RAID array that needed to be preserved) from 12.04 to 14.04 in a bit over an hour. The hard part was backing up the most important bits of data. The actual upgrade was painless...except for the corrupt USB-key I made the first attempt with.
We didn't really image Linux machines because they were generally back-end servers, but it was something I looked into with some depth. Basically, because of the effort Canonical put into supporting Ubuntu on VMs, it was a piece of cake. I was actually more interested in network booting ala the Linux Terminal Server Project, but the truth is that I would have been drawn-and-quartered if I put any distribution of Linux onto a machine when a teacher didn't demand it. The teachers ran the show. A situation that was mostly fine, but horrible in some areas (ie. security).