The fact is, even a single user may to access cups (at http://localhost:631) with Safari or whatever, occasionally.
I bought a DYMO DiscPainter, installed all software, updated to latest. Wouldn't work (stuck at "rendering". Googled the error message I was using. Turns out you had to "modify printer" from the CUPS localhost site, correcting it to "generic USB" device. Bang. Printer works.

My girlfriend has an Epson CX8400 all-in-one. It stopped printing at some point. Reinstalled correct Epson drivers for her (10.4.11) computer. Didn't work, but her printer worked perfectly with the latest Epson Leopard drivers (I'm running Leopard on my computer). So installed "Gutenprint" (i.e. 3d party) on hers. When adding the printer to her computer used "Cups EPSON 8400 + Gutenprint" (instead of just "EPSON CX8400", which was the first choice). Guess what, the thing starts working, even through airport extreme.

The moral of the story "messing" with CUPS and installing "3d party" versions sometimes does the trick when nothing else will. If by "messing with CUPS" one means compiling the latest source code and installing on one's system, I have to agree. I did this once. It held up until the next security update. That update so hosed my (modified) printing system I had to do an archive and install. (I did the compiling because Apple's version of CUPS is always behind the main one, and a lot of what they do is security fixes. One has to assume Apple is handling these security fixes in some other manner. Or at least one hopes they are (they now OWN CUPS, after all!). Certainly they don't bring out the latest version of CUPS as they come out (same thing with JAVA). You have to wait for them to get around to it. I find this irritating. I love Apple, but they are control freaks.

Don't do things for the hell of it, but if you know what you're doing, having some rudimentary knowledge of your computer's software and printing architecture can be a good idea...and sometimes you need bigger interventions, like this software.