I would summarize my experience with this in 2 words "does not work". ok, it's 3 words. All the clutter about "can't do such and such".
If still unsure - take a look to autopackage FAQ section "I bet autopackage sucks because ...". Yes, you right, it sucks. And plenty of reasons why.
The main line is following: you can't mix more then 1 install-managing systems in single computer without having "fun" of manual conflict and/or dependancy resolving.
Every time I see something like this I'm thinking - WTF does those folks think ?! What is this magical thingie that convince them that their package system XYZ is better then 3 already existing (RPM, debian, gentoo) and others that I'm not aware of ?
"Distribution neutral" ?! What's a weird idea ! Who says that RPM is not ? Go ahead, compile rpm (or apt-* or ebuild) on your platform and I bet that you will have same effect.