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