To me this is a very simple question to answer. Linux does not need a unified package manager when the source to the application you are using is available for you to compile on your own. Make your own package.
“Now Dann,” you might say: “Surely you do not mean for generic desktop user Joe to compile his own software?” To that I reply: “If not him or her, then surely there is someone else in the community willing to help him or her out.”
Yeah, it may be a bit of a challenge for someone to learn how to compile their own software and/or make it into a package. I understand that. But there are thousands of people out there who can, just ask them. Those of you who can, step up and assist when you are able. That is a simple way you can contribute; so consider it.
Generally, most of the software you could want will be available for the major distrobutions. Ubuntu, Fedora, Mandriva, and OpenSuse all have pretty big software repositories, chock full of software choices for the desktop user. But should you find a piece of software you want not in your repository, having access to they source negates the need for a “standard package format” since you can compile and install the software yourself; even making a package for your system if you so choose. It is only when the software sources are not available, when the software is not Free or open that the package format debate comes into play.
Case in point. I wanted gwibber for Debian Squeeze. There was no package I could find, but the sources were available. So I pulled them down from launchpad, compiled the source and in less that 5 minutes was up and running. Had gwibber been closed source, I would not have had that capability. I would have had to use a tool like alien (which is a fantastic tool) or tried to force install the Ubuntu package. Both avenues court failer and jeopardizing the system and package manager stability.
Would it be nice and convenient to have a package format that installs on Debian, Ubuntu, Fedora, Slackware, Arch and Gentoo? I could see the benefit of that; but then again that would require all those distributions to be library compatible. I do not find that appealing. I am not using Linux for convenience, I am using it because of it”s flexibility and power. Having access to the source provides that to me.