Well, since you asked....
They put two different binary installers in and one of them will crash and the other one won't and the readme doesn't explain the difference between them.
The Linux binary installers are not "intelligent." If you are replacing an old version (which, face it, nearly everyone getting it from their site would be), they just wipe out the entire directory (rm -rf) that the old mozilla was installed in and put the new mozilla in over it. They don't tell you this.
Plugins then become more of a pain in the neck. Sure, you can backup the plugins directory somewhere else (like /root) before running the installer but that's an easy thing to forget (especially since the README and the installer don't mention this). If you do forget, all plugins have to be reinstalled by hand.
And you will be royally hosed if you happened to put the old mozilla in, say, /usr/bin instead of its own directory (something else the installer doesn't warn you about, unless that's changed recently). This hasn't happened to me, but has to others.
You are right, they are not all that bad, but losing all my carefully installed plugins a couple years ago soured me on them. Plus, I really like having my linux software organized with the RPM database.
[ September 15, 2004: Message edited by: M. O'Brien ]