Pope Paul VI wanted to make the Ordo as acceptable to Protestants as possible, without changing its nature.

Therefore, there are no essential differences -- because to have changed its nature would have made it no longer what it has always been --

Nevertheless, I propose the following experiment:

1) Ask a Lutheran pastor if he can use the Ordo of Paul VI. Odds are that he can, because there is no genuflection before showing the Sacred Host to the assembled lay faithful in the Ordo of Paul VI.

2) Offer a die-hard neo-con the chance to attend Mass in the Extraordinary Form or miss Mass. Chances are that he will miss Mass, because it won't "feel" as if he's been to Mass; or, he'll say "it's nice for a change of pace, but I wouldn't want it every week">

I would agree that much of the issue between the old and new rites had to do with the way in which they are celebrated. Fr. Peter Stravinskas, for example, has said that if the new rite had been celebrated without some of the innovations we've seen becoming common in the past 40 years, i.e. things which were never mandated for the rite but were almost universally done as if they were - priest facing the people, substandard or other wise inappropriate music, liturgical experimentation and abuse, etc. - there would not be such liturgical controversy today.

At the same time, minimalist and even sloppy liturgies were certainly not that uncommon before Vatican II (and of course low mass was the overwhelming "option"), so the issue cannot be reduced simply to how they are done.

Even if the new rite is done with all the "traditional" options - Latin, ad orientem, chant, sung prayers and readings, etc. - there still are some significant differences between it and the older rite. The calendar and the lectionary are two obvious things, but there are many others that are more subtle, but can make a big difference over time. For example, the in the old rite, the collect, secret and postcommunion all end (as a rule) with the full Trinitarian formula, whereas this is retained only for the collect in the new rite. And many of these prayers were edited or changed entirely (not to mention the prayers, such as those at the foot of the altar, which were omitted altogether).

Most of these changes are not that noticeable if you attend a mass in the old rite once or twice - after all, the bigger outline of the mass is the same. But these things can grow on you and become quite formative if you go every week for a year or two.

The second reading on Sundays was never meant to be connected to the first reading or the gospel - it is a continuous reading from St. Paul (or Acts in the Easter season) - so perhaps you were looking for a connection that wasn't there? And I never thought of a connection between the collect and the readings, given that the latter are on a three year cycle. So I never looked for a connection between these things in the OF (though there's almost always an obvious connection between the OT reading and the gospel.)

I agree with the maxim in this case: three readings and a responsorial psalm are simply too much to assimilate in a single liturgy. Plus the association of a set of readings with a particular day has been lost.

I always been bothered by the sung propers in the OF, at least those in Ordinary Time, on account of the fundamental "disconnect" within the texts of the liturgy that you allude to. Although most of the sung propers were transferred intact from the old rite, the new rite has different readings and prayers, and so the interconnection between these elements - sung propers, readings, prayers - has been lost.

Singing the propers in the OF is wonderful and certainly preferable to singing only hymns, but like many things in the OF, they are an attenuated version of their former selves. The integration between the prayers, sing propers, and readings has been retained for the great feasts, which is why these can be so satisfying in the OF.

Can someone explain: would Lutherans object to genuflecting before showing the consecrated Host to the people, but not mind doing so immediately afterward?

There are many Lutherans who wouldn't mind it. I've visited a Lutheran church before which essentially used the Pian Missal.

If only Bugnini had thought like you..