I'm upstream for pptp-linux and pptpd. I had cornered Mark at a linux.conf.au some years ago complaining that Ubuntu were fixing things and not passing anything back to me, and he said he'd look into it.
Your article here has encouraged me to have a quick look ... the Ubuntu bugs for pptp-linux are quite extensive, and I feel cheated, I didn't know there was such a rich body of input for me. I'll be busy for some time now. I only wish they had been passed upstream more slowly!
Hint for upstreams ... create an account on launchpad and ask it to deliver you bug reports. Do Ubuntu's work for them. Ignore the bugs that are obviously distribution specific. Run multiple bug trackers. Sigh.