Fairly realistic in concept, but overly simple and pushed to an unlikely extreme. The concepts were probably simplified on purpose to make it an easier read, or perhaps incidentally because Orwell only understood the topics on a superficial level. The latter is something I doubt, but is a possibility worth considering.
Mass surveillance on the level described in the book was not possible in Orwell's time, but is certainly possible in the modern era. The idea behind it was that everything you are doing is being recorded, but not necessarily watched; it would be impossible to have every single person constantly watched. Instead, it was the threat of being watched that kept people in line, and you can already see that kind of thing in effect today. How many opinions have been self-censored due to fears of being put on an NSA watch list or, for a less extreme consequence, shadowbanned on Reddit? I hear now and then that people do not want to voice their opinions online because of such fears and the fear of their thoughts being on a permanent record.
Room 101 is brainwashing through torture, plain and simple. This has been happening for centuries. The concept was not pioneered by Orwell or the totalitarian governments he was criticizing. Medieval witches would be tortured into confessing their "crimes" and then executed following their "apology." Very similar to the ending of the book.
The Party, and especially the personage of Big Brother, has not really manifested itself anywhere in the world except in North Korea, where Kim Il Sung still has his portrait hanging in every schoolroom across the country. The position of President was abolished upon Sung's death, making him the "Eternal President of the Republic" forever. He is, in essence, a very real Big Brother.
The eternal wars, with the flip flopping between enemies and allies, was something really only endemic to the twentieth century, and did not happen exactly as Orwell predicted. Rather than three powerful factions being always at war, only two really engaged each other, and while their fighting was indeed nearly constant, the use of nuclear weapons and willingness to engage in direct combat was not quite as pronounced as Orwell presumed it might be. Alliance realignments have not been as frequent either, with only one happening thus far.