"As I said, the whole Polish foray generally"

And I just said that you have mistaken one war with another and corrected this mistake. That is all.

"you have yet to present anything to make the Polish army (or at least the cavalry) appear any less fundamentally feudal in nature - the very fact that its linchpin are landed noblemen and similar potentates is alone enough to mark it as such. That, according to your description, the cavalrymen were at least partially mercenary is nothing new in such setups"

No they didn't have to be landed noblemen. It didn't matter, they had to be:
1. well known,
2. experienced,
3. wealthy ( sometimes not necessary),
That is all.

And they were COMPLETELY 'MERCENARY', but I don't think calling them mercenaries is really correct - they were rarely fighting outside the country actually. There were no Husaria mercenaries for example.

"The part about the "equal rights" of the nobility would appear to hint at something many sources I've seen speak of - the enormous military importance and therefore political influence (the coëfficent between the two being a typically feudal trait) of lower landed aristocracy, whom at least one source referred to by the term szlachta or thereabouts and added "famed for their courage"."

One thing to correct.
In Poland there was no higher or lower aristocracy. According to the polish law all these titles ( baron, count, prince, duke etc.) didn't matter. Actually NOONE was allowed to use this kind of ranks nor grant them.
Exceptions:
1.former Lithuanian/Russian 'kniaz' ( princes) were allowed to use these titles;
2. ranks granted by the HRE Emperor, Pope could be used.
However all this didn't matter in courts or enewhere else.
So in theory a landless noble from a small village in Masovia was equal to a Ukrainian noble with 5000 strong private army.
Of course in theory, but today it isn't very different in a way.

'Szlachta' is the term used to describe all the nobility of the country/region - more than 10 % of the population ( in some regions even 33 %).

The most important part of this class was middle 'szlachta' which prepared most of many reforms, but also very wealthy nobles achieved a lot of good.
In many ways In Poland middle nobility was replacing citizens preparing similar reforms.

"All the better that way - states that rely on such systems quite often did so out of sheer inability to sustain an economy that allowed for alternatives (which, in other words, require a comparaticely sophisticated economy and a central governing organ capable of gathering taxes and pooling them for whatever use required, such as a standing army)."

In Poland there was another reason. It was to prevent the king from becoming a tyrant, because the army was often his tool for keeping his
'beloved' country in check.
It was also because this way unwanted wars were rather hard to start by a monarch - these guys should really be controlled.
I think it was a good solution.

"That aside, compared to the ultramodern Swedish army of the mid-1600s the Polish one was little more than a curious if still dangerous medieval relic. Englund, who seems fascinated by the collision of old and new military paradigms (he is clearly aware of the often tragic nature of the friction, and his tone is often almost wistful - gallant old individualism vs. faceless modern efficiency seems like a recurring theme in his books), may be excused if he bluntly calls it such especially in the context."

Was it ?

I can't see no 'old individualism' in Polish army. Sorry it can be only found in the way how it was possible to achieve much of 'wealth and glory' in the Republic. You can call it 'the american dream' of that time.
It was a republic, so much more was possible than in countries ruled with 'an iron fist' even when covered in a gentle glove.
Certainly it is rather hard to see much individualism in the way how the army fought on the battlefield - no 'knights errant' but units moving, charging and fighting in a formation, which very important in Polish military art.

"Off with the finger-pointing, thank you."

Sorry, but it was just an example, if you are from Sweden I am sorry if it offends you.
I just wanted to point out that many armies of that period were dependant on loot. Sweden is a very good example, because here 'the war had to pay for itself', so in many ways loot was more important than in other countries, or not ?

"The lance was always quite possibly the most disposable part of the feudal cavalryman's outfit in any case - its sheer lenght and the one-handed technique of wielding it made it cumbersome in the melee that often followed the initial shock charge."

But it was worth using it, especially against enemy pikemen. When it wasn't really useful ( rarely) it wasn't IN USE, that is all.
In addition the lances were always provided by the country in the same way it was done in the XVIIIth, XIXth and XXth centuries.
Was the cavalry still feudal at that time as well ?
BTW - even in the XXth century some units were created by local landowners/other wealth men in Poland, maybe it was because Poland was/is feudal at that time ?
Or maybe the reason was different...

regards Cegorach/Hetman