Having now watched the whole thing, I find it less onerous. The first hour and a half or so is just too full of prolonged set-up sequences. It's like if the first 1.5 hours of the LOTR movies was like the FOTR movie's prologue.
Once things finally come together, it starts feeling like a movie rather than a stream of consciousness exercise or like reading the Old Testament. I'm glad Snyder got to make this version, and give everybody the story he had in mind originally. It's a weird beast of a movie-like-thing.
I can't think of any movies that have been in this strange state; To be halted due to a terrible tragedy, and to then have another director come in to finish the movie, only for the original director to come back and do a 4-hour long cut of his version of the film, post theatrical release. It is nuts.
That said, I feel that sometimes movies are cut down for dumb reasons, and to the detriment of the quality of the movie, while other times movies are just way too long and desperately need cuts. I'm looking at you Peter Jackson!
The Hobbit Trilogy for example, did not need to be 3 movies. It could have been easily trimmed down to 1 movie, and it would have probably made for a better movie to boot.
Cutting Saruman's death from Return of the King was a crime, and left a bad taste in my mouth, considering how much filler there is in that movie. Plus it felt like a trick to motivate people to buy the extended cut on DVD. Plus the extended editions add more meandering scenes to the Two Towers with Treebeard, which jarringly interupt the action several times. Seeing more of Middle Earth is a nice novelty, but it comes at the price of pacing. So I find myself in the odd position of both liking the extended cut for 1 or 2 scenes, and hating them for the filler, long run time and bad pacing.
Aliens Special Edition includes some wonderful scenes that I really think should have been included in the theatrical release, but not all of the scenes that are now in the special edition. There is way too much exposition in the special edition, which spoils several of the movie's surprises. Plus I don't think we needed another scene of Newt's high pitched screaming.
Kill Bill was clearly intended to be one movie, and not two volumes. But frankly, I like that it is two movies. Tarantino may have added some filler here and there to pad out the runtime for both movies, but I like most of what he may or may not have added.
With its 4 hour run time, I think Snyder's cut could have easily been made into 2 movies.