I don't know if Dillon changed to seat-only (no-crimp) dies before or after they added the "quick-clean" feature. BTW, Hornady seating dies also have that same easy disassembly feature, without affecting settings, plus optional micrometer seating depth adjusting screws.
The Dillon "magnum" powder measure I'm speaking of is an entire powder measure, not just a "magnum bar". I think it was developed from the powder measure on their shotshell progressive press. This is not a free upgrade from Dillon either.
As far as micrometer adjustable PM inserts, Dillon does not give those away for free either.
The design of the 550 primer bar has changed shape from flat bottom, to chevron grooved bottom, to cast, "hollow" bottom, with teflon-coated and non-coated versions mixed in along the way. Dillon does provide latest-style replacements for free.
The Hornady shell plates are interchangeable from projector and LNL-AP presses. I'm not positive, but I think the casefeeder compatible subplate and new primer system for the LNL-AP are also compatible with the projector. At a cost, not unlike upgrading from the Dillon 450 to the 550.
Dillon did not originally include low primer warning systems with their presses, but now they do. Do they give them away to older press owners (I really don't know)?
Both the old and new (casemouth expanding) Hornady case activated PM linkages are compatible with the projector, but you do have to buy them. The Dillon PM linkage upgrade is a safety-related upgrade (I've heard they will not send you the parts to go back to the old spring-return version, you have to modify them yourself), probably provided at no cost in order to avoid lawsuits. The Dillon "upgrade" is not an additional-capability upgrade, as is the new Hornady PM linkage. When Hornady rolled in the new expanding PM linkage on their presses, they increased the price of the press accordingly. Do you really think they should give it to buyers of older, less-expensive presses for free?
Andy