Hi ..
Yeah ... I wouldn't want to ruin a good thing either. You're the mom. And, every baby is different. Some babies can probably be swung to sleep and not develop a habit. And even if a habit ensued, I personally believe there comes a point where if the baby's reeeeaally sleep deprived--you've just got to get her/him to sleep, at all costs. I also think that if/when other factors are present (colic/reflux)--there's a different set of rules because the baby is in pain.
Tracy's and Mr. Karp's approach are based on the same brain research. They just emerged with slightly different methods. It seems to me they really only depart from each other on 2 points:
1)Tracy replaces the 'S'winging with 'P'atting; And,
2)I think Tracy seems to differentiate between what you do to "calm" the baby--versus what you do to put it to sleep. For example, she absolutely advocates sucking/pacifiers for calming (whilst also swaddling, white noise ...). But, Tracy would probably advise mom's to remove the paci before the baby falls asleep. Because you can end up with babies that cry every 30-40 minutes to have someone come replace the pacifier.
But those tendencies to develop habits are unique for every child. And some can fall asleep with a paci--and not need it to be later replaced to advance through sleep cycles.
My gathering from Tracy's writing is that the reason the patting isn't enough for some (not necessarily you) is that it's supposed to be more firm, and rhythmic than some apply it. I think when it's done they way she would do it--it can directly replace the swinging 'S' Karp recommends in HBOTB (Happiest Baby On th...). However, again, not every child will become reliant on swinging to get to sleep anyway.
Really, I'm just glad you found something that's getting your LO some good sleep. It must be such a relief. And, sleep--and this age--is SOOOOoooo important (for the baby and the entire household).
Good luck!