They've omitted the internal monologues, which without seeing it I have no idea how much difference impact there is but that feature was quite a main characteristic of the series. Also apparently some say the Kiss-shot subway scene is pretty intense in a horror way. Some japanese comments found on /a/ (had to remove the kanji original comments as fj don't allow it, and line-break limits ugh...)

550: It looked gorgeous but the story was hard to follow, felt like it jumped all over the place
553 :Acting-wise you had the tried and trusted 4 people.
The BGM had lots of that scat...-ish... whatever-it-was. I found it somewhat repetitious but that's just me
CG nowadays is pretty amazing
The live-action bits were on the restrained side, but they were there
With the **** he did it's ******* nuts that Oshino isn't as strong as Kagenui
557: Can't really call Hanekawa the "hidden titty monster" any more.
So it was a cherry tree.
It was early morning but the theater was 70% full.
8:2 male-female ratio, youngest was teens oldest I saw someone who looked in his/her 50s.
Mostly twenty-somethings, as expected.
559: Watched it first thing in the morning but it looks like the trilogy will flop
566: Just saw it. Not going again but I will buy the disc.
Kiss-shot's entrance scene was left me a bit scared, it was pretty horror. Waiting 'til summer is gonna suck.
569: They were right to leave out the monologuing.
Actually they aren't really needed in the rest of the series either.
573 >>550 (the guy who thought it jumped around a lot): Without the monologues, Araragi's emotional changes do feel sudden, don't they?
580 >>569: Araragi's monologuing in Bake ep 1 gives me goosebumps.
581: Guess I'll have to learn Italian before the next part.
582: 63 minutes is way short I thought, but it was so rich I was left feeling full.
587: "Nekketsu-hen opens this summer." So some time around November, then?
592: The text cut-ins did a good job at explaining and expanding things in lieu of the monologues.
Though, the French and Morse code is probably a bit harsh for a first watch.
593: I haven't read the novel but did it have the Morse code in it?
590: If were talking things that can't be aired on TV, the seal penis from Yaruki Manman showed up when Araragi, excited by Hanekawa's panties, went to go buy porno.
625: I hardly thought "this looks amazing"
Though there was a few parts drawn cute, or pretty.
It may have been more than TV quality
but I didn't feel it was up to theater level.
The script, the acting, the placement of time were all somehow a little off in a lot of scenes, and the pace wasn't very good.
I couldn't help but think they sacrificed the first part
in order to make it a three-parter.
670 >>625: If you couldn't think so from that, then there is something seriously wrong with your film-watching eyes.

I know i'm gonna love it though