IMO: It works well as a live or USB distro. KDE3/Trinity is fantastic - much nicer IMO than KDE4, and can run on much slower computers.
However, the package management is not so great - the combination of compressed modules, packages, and Slackbuilds leads to redundancy and brokenness, not unlike the Puppy Linux package management system. I don't think it's suitable for installing to the hard drive; which is a shame, because (again) Trinity is great.
P.S. Despite it's better performance than KDE4, Trinity is still a bit of a RAM hog. If you're running Porteus on a machine with less than 512 MB of RAM and no swap partition, you should probably enable zram.
(Actually, if you're using any distro with a recent kernel on any computer that can run it, you should probably enable zram. But that's another matter.)