ChrisW wrote: “I'd respect a definitive showing of instances where the presence of features/limitations are indispensable in a claim preamble …”
I underscore the two words because, one, if I understand ChrisW’s request, a “definitive” showing is IMO simply not possible because the patentable weight of recitations in the preamble is a fact-sensitive inquiry - plenty of authority on that - and depends on the procedural posture of the case (construction of a presumptively valid allowed claim or not presumptively patentable claim in prosecution?). Or it depends on the specific issue involved (non-analogous art ? claim construction? “pertinent prior art” for foreseeability of amendments for DOE estoppel analysis?). And two, as a personal view, the “indispensable” stuff belongs in the body of the claim, not left to judicial whim whether such preamble recitations do or do not breathe life and meaning into the claim.
A different thread dealt with “statements of intended use” recitations (e.g a widget for …). If I recall, the overwhelming consensus was: just don’t do it. Rightly or wrongly you are begging for a fight with an Examiner. If you are in the mood for a good fight and your client has enough bucks to go to appeal, maybe all the way to SCOTUS, then do it! Otherwise, rewrite that “for” clause as an adjective, or find someother way. At least you potentially limit the “pertinent prior art” (Duramed v. Paddock). Per my prior post in response to JimIvey's question, other kinds of preamble recitations may be treated more kindly in litigation, if they were successfully relied on before the Office.