I've already written my pieces about Best Film Editing and Best Sound Mixing, but it bears repeating:
These categories are really freakin' tough to predict. More so this year than usual.
Whiplash has the type of editing style that frequently wins Oscars, but have enough voters actually seen the scrappy Sundance alumnus that barely passed $10M at the box office? How many Academy members are buying the "12 years of footage" byline in Boyhood? American Sniper is certainly the wild card in the category and I may stick with it as my final prediction (hey, you need to allow yourself at least a few against-the-grain guesses), but it'll be a game time decision.
Best Sound Mixing is an equally frustrating three-way race. The driving musical rhythms of Whiplash certainly stand out, but it's a question of how many voters have seen it? Don't let J.K. Simmons' domination of Best Supporting Actor fool you; There are a ton of people who will vote for him without having seen his performance (dude's beloved). And will the sound really jump out at people on screener? Birdman has brilliant sound work that excels by not drawing attention to itself, but neither did the likes of Hugo or Slumdog Millionaire. And American Sniper looks strong in sound editing, so how does it makes sense not to predict it here, given how rare splits are?
All of this is simply to say: Don't be surprised if my prediction sidebar toggles back and forth on these categories over the next few days. I'm also having similar debates about Best Foreign Language Film, which I'll address tomorrow.
[UPDATE:] I'm also reneging on a couple of my initial thoughts in the shorts. All will be finalized by Sunday morning at the latest.