Astrologer50 et al., re: intercepted houses in Placidus...
I used to dismiss them as make-work chart factors, also, till I began to re-think them based on (a) my chart and (b) other people's charts. The best way I can put it is that:
1.) A planet in an intercepted house just doesn't get a lot of "traction." Its sign and aspects may suggest some strong potentials for the person, but these just don't seem to happen in the persons's life. The energy gets overshadowed, such that a person may not get the recognition, benefits, or fulfillment from those planets that you would think.
I don't think this is a huge issue if, say, Neptune is intercepted; but if someone's sun is in an intercepted house, it can make a big difference.
Basically I am a pragmatist. If something seems to work in astrology, I would like to use it, even if it takes a little extra time.
2.) I work extensively with "accidental rulers" of house cusps. I. e., if someone has Gemini on the cusp of the 7th house, then I would look to Mercury's house location and aspects to help get a handle on that person's long-term relationship potential. A great book on this technique is by the respected Dutch astrologer, Karen Hamaker-Zondag, The House Connection. What happens, then, if you have intercepted signs (and if you have one, its opposite sign will also be intercepted) is that you have planets that don't rule any house cusps (like Uranus if Aquarius/Leo is intercepted) or that rule one house cusp rather than two (like Venus if Taurus/Scorpio is intercepted). This phenomenon can strengthen some planets in a chart (they're "doing for two") and weaken others.
iwonder, if you you use a house system where the angles fall within signs but not on house cusps, I think you would just treat them as sensitive points, with the same meanings as usual (MC=public image, vocation.)
Sundance Kid, if you find the same results with several different house systems, this is good news because, even though the cusp degrees will vary, you basically can read your planets' house placements with a lot of confidence.