"Almost" leaves out the significant disagreements, from papal infallibility and power no less, to difference in their Biblical canon.
"The Orthodox Church opposes the Roman doctrines of universal papal jurisdiction, papal infallibility, purgatory, and the Immaculate Conception precisely because they are untraditional." Clark Carlton, THE WAY: What Every Protestant Should Know About the Orthodox Church, 1997, p 135.
The Orthodox Church does not believe in purgatory (a place of purging), that is, the inter-mediate state after death in which the souls of the saved (those who have not received temporal punishment for their sins) are purified of all taint preparatory to entering into Heaven, where every soul is perfect and fit to see God.
Also, the Orthodox Church does not believe in indulgences as remissions from purgatoral punishment. Both purgatory and indulgences are inter-corrolated theories, unwitnessed in the Bible or in the Ancient Church, and when they were enforced and applied they brought about evil practices at the expense of the prevailing Truths of the Church. If Almighty God in His merciful loving-kindness changes the dreadful situation of the sinner, it is unknown to the Church of Christ. The Church lived for fifteen hundred years without such a theory. — http://www.goarch.org/ourfaith/ourfaith7076
Vladimir Lossky, a noted modern Eastern Orthodox theologian, argues the difference in East and West is due to the Roman Catholic Church's use of pagan metaphysical philosophy (and its outgrowth, scholasticism) rather than the mystical, actual experience of God called theoria, to validate the theological dogmas of Roman Catholic Christianity. For this reason, Lossky argues that the Eastern Orthodox and Roman Catholics have become "different men".[18] Other Eastern Orthodox theologians such as John Romanides[19] and Metropolitan Hierotheos[20][21] say the same
Roman Catholicism teaches, also, that, in the Age to Come, man will, with his intellect and with the assistance of grace, behold the Essence of God. The Orthodox declare that it is impossible to behold God in Himself. Not even divine grace, will give us such power. The saved will see, however, God as the glorified flesh of Christ.
According to Metropolitan Hierotheos that because the Roman Catholic Church uses philosophical speculation rather that an actual experience of God to derive their theology they are lead into the many errors that Orthodox call into question about their theology including the filioque[66]. More
I was shocked to find out that the dogma of the Immaculate Conception (which asserts that “from the first moment of her conception the Blessed Virgin Mary was, by the singular grace and privilege of Almighty God, and in view of the merits of Jesus Christ, Savior of mankind, kept free from all stain of original sin”) was defined only in 1854 by Pope Pius IX in his bull Ineffabilis Deus. The dogma was only a little over a century old! And I found it futile to argue that even though the definition was late, the teaching had been universally held beforehand. Not so! Right up to the very time of the definition, various parties contested its orthodoxy. ...
I sadly concluded that the erroneous Roman understanding of original sin had led to another erroneous teaching, the dogma of the Immaculate Conception. The dogma was clearly an unwarranted innovation .
It was much the same with the dogma of papal infallibility. This doctrine asserts that when the pope speaks ex cathedra, “from the throne,” or officially, on matters of faith and morals, he teaches infallibly. Thus the whole Church is bound by his teaching. - Orthodoxy and Catholicism, “What are the differences;” http://turretinfan.blogspot.com/2009/12/lay-roman-catholic-and-eastern-orthodox.html
Pope Boniface VIII, Unam Sanctam: “We declare, say, define, and pronounce [ex cathedra] that it is absolutely necessary for the salvation of every human creature to be subject to the Roman Pontiff.”
"If, therefore, the Greeks or others say that they are not committed to Peter and to his successors, they necessarily say that they are not of the sheep of Christ, since the Lord says that there is only one fold and one shepherd (Jn.10:16). Whoever, therefore, resists this authority, resists the command of God Himself. " — Pope Boniface VIII, Unam Sanctam (Promulgated November 18, 1302) http://www.fordham.edu/halsall/source/b8-unam.html
Furthermore, in this one Church of Christ no man can be or remain who does not accept, recognize and obey the authority and supremacy of Peter and his legitimate successors. Did not the ancestors of those who are now entangled in the errors of Photius [the eastern “Orthodox” schismatics] and the reformers, obey the Bishop of Rome, the chief shepherd of souls?...Let none delude himself with obstinate wrangling. For life and salvation are here concerned...” Pope Pius XI, Mortalium Animos, PTC:873) The Promotion of True Religious Unity)
“to difference in their Biblical canon.”
There are no canonical differences. I suggest using actual Orthodox sources and not protestants talking about the Orthodox.
As for Ineffabilus Deus - it’s the formulation of the doctrine which has been taught long ago.
“All these things our illustrious predecessor, Alexander VII, summed up in these words: “We have in mind the fact that the Holy Roman Church solemnly celebrated the Feast of the Conception of the undefiled and ever-Virgin Mary, and has long ago appointed for this a special and proper Office according to the pious, devout, and laudable instruction which was given by our predecessor, Sixtus IV.”
This was written in the early 15th century - so the Doctrine was quite old then.
http://www.papalencyclicals.net/Pius09/p9ineff.htm