I installed KPackageKit a few weeks ago and have used it as a "Synaptic replacement" so far, installing updates, packages, etc. It works well for this purpose (and looks better in KDE than Synaptic since it is a KDE/QT front end). I am going to try it out for installing other types of packages and I will report the results. I think it's a great idea.
FWIW - I agree with the poster above. Here's a real world example: you try out KDE CE. You think it's kinda cool. You find there's a great website called http://www.kde-apps.org/
and you explore it. "OMG look at all these cool apps here. And Plasmoids! And themes, and......". SO you want to install a few of them to try them out. But then you notice there's not a .deb in sight. So, you roll up your sleeves and say to yourself that you can do this. You can surely read and follow directions in the unzipped download's readme file. You read and execute "cmake packageXXX". It doesn't work. Oh wait, cmake is not installed by default in Mint / Kubuntu. By now, 90 pct of that "coolness factor" is gone. But 10 pct of you are brave and plow onward. sudo apt-get install cmake gets the job done. Compile...wait..wait..wait...error
. Apparently you need some *-dev files in addition, however it is unsure what ones you need, since what they are called (and whether they are installed or even available or not) depends on your distribution.
We know that compiling from source can be a PITA sometimes even for experienced users. Imagine a noobie Mint user who is smart enough to conclude "If I'm running KDE, why can't I use these apps listed on KDE-apps.org?????"
. So they ask a question in a forum and get all the various answers we all know they will get about distributions, "flavors of Linux", packages, the said benefits of DEB, RPM, PISI, PUP, etc etc
depending on the forum they are in.
At this point they will either likely give up, or keep plodding ahead. But most people will say "screw this I only wanted to see that cool looking weather app, it's not that important anyways". And then move on.
My example is just one of 100's out there that can lead a novice user to the same conclusion. Sites like get-deb.net are a good start, however they have very few (in the grand scheme of things) applications. And they are Ubuntu (read: not Xubuntu, Kubuntu, etc.)-centric only.
I hope application packaging continues this evolutionary track it is on. It can only benefit us all.