Looks good John, I like the upgrade instructions
I ran into the same problems you did with Dan Browns PHP 4.3.10 RPMS - some message like 'No version found - regenerate configuration' in horde stup and when you clicked on it, it either went nowhere using firefox, or to an error page using IE. I did get it working with the 4.3.9 RPMS from Laurent Dinclaux.
A note about the fileinfo bit - you need to add/edit a custom template to add 'extension=fileinfo.so' in php.ini next to the others and restart httpd.
Also from my experience following your upgrade instructions, you assume people have nag, mnemo and kronolith installed, where they may not - so you have to use the install .sql file, not the upgrade one.