I also based my time estimates for someone who was going to build from the source code, not use RPMs (since you only mentioned UNIX in a generic way). I've never used the RPMs mostly because I tend to compile my security and web software from scratch anyhow.
The RPMs apparently make it easier, but quite a few Linux newbies don't quite understand the concept of software package dependencies. Again, lack of UNIX knowledge is a hindrance that really can't be estimated well. Also some people eventually figure out how to type "man rpm"; others apparently can't find those keys on their keyboard.
I'm not surprised that Cathy found the RPMs very easy to use. On SGI IRIX, inst is the command line installer, and the concept of software dependencies is very clear to anyone having IRIX experience. (I know: when I gave up my Indigo2, it had IRIX 6.2 + >60 patches.)
