Don't confuse, I'm not distributing any unofficial OpenBSD iso, and I don't need to!
I used to create the OpenBSD iso myself because there's no official iso from OpenBSD team, you can find how I did it here. But with the arrival of OpenBSD 4.2, you no longer need to use mkisofs or mkhybrid to create the iso from the files that you download from any of OpenBSD download mirrors, I was stupid enough to download everything from here -
I couldn't find cdrom42.fs in this release so I can't create my own iso. In fact now what you actually need is the install42.iso, just burn it to the CD and you are ready to install OpenBSD 4.2.
It's time to install the fresh puffy!