Well, I might as well wade in too
I've run Sid for years. You've got a bunch of great advice here and it'd be wise to listen to it. I would take exception to TFA you linked, though. I can't think of any reason why I'd map an Ubuntu PPA to Debian and I think that's a horrible idea.
I do have a four or five non-Debian packages on my machine and what I do is download the .deb, extract it and read what package dependencies are; if I can meet those dependencies I install the package
without editing apt sources. Alternatively you can just grab the .deb and try installing with gdebi (I never have learned to love aptitude). gdebi will tell you if dependencies are missing. I also avoid deb-multimedia as I had a package there break Sid almost a year after I installed it.
I will say that apt-listbugs has saved me a couple of times - IME the biggest problem I have with bugs is in chromium, which I believe needs a little more testing before being made available in Sid. apt-listbugs won't save you from a zero-day vulnerability but I do have it configured to report important and higher bugs instead of the default serious and higher. I get a little more information that way.
I also subscribe to a couple of Debian dev mailing lists and their bugtracker so I can see what's coming down the pipe, I get a couple hundred emails a day from the lists but usually all l have to do is read subject lines to find out what's going on. I use a mail rule to dump list mail into its own folder so it doesn't clutter up my email
Most important - understand what apt wants to do to your machine and if an upgrade doesn't look safe, don't upgrade. The problem will normally be fixed in a couple days or so
cheers -