Crikey said:
Heh. When I bought my G4 tower, it had 10.0 installed but came with the CD for 10.1; I installed 10.1 right over the top of 10.0 and it worked great. Then 10.2 came out, and I installed it right over the top of 10.1. Then 10.3 came out, and I installed it right over the top of 10.2.
Heh... that sounds like me. I did exactly the same thing with my old G4 tower (except I installed 10.0 the day it shipped), except at the point of upgrade between 10.2 and 10.3 I also moved the OS to a G5--cloned 10.2 to the G5's drive, then installed a straight 10.3 upgrade right on top of it. Never even did an archive and install.
Worked great except for this one little glitch that, so far as I could figure from the three other people in the world who reported it, only occurred on G5s that had been upgrade-installed from 10.2 to 10.3 and had over 2GB of RAM. And even that was just a minor annoyance.
10.4, I did finally do a completely fresh install and use the migration thingy to move my users over, but I doubt even that was necessary.
So no, I wouldn't get too worked up about reinstalling unless there's a very good reason. If you particularly love system hacks (as opposed to just a lot of apps), then eventually you might screw something up badly enough that an archive and install is required, but even then I'd only do it if there's a specific reason for it.