I'm surprised by these "hard to hear the dialogue" comments (though I don't doubt that these experiences occurred). I was able to hear the dialogue in this movie pretty well (considering the roasting I got
in the Star Trek thread where I was one of a few that complained that dialogue and associated sound was on the low side).
The TF2 audio is like the polar opposite to ST audio, per my experiences with the movies on my gear. ST required a substantial boost of my volume knob to make it appropriately loud, and then a twist more on top of that to bring the dialogue level to a natural level. TF2, otoh, was just effortlessly loud on my system with no special adjustment at the volume knob, whatsoever. Dialog level just always came in at an easy level for me to pick-up. The peaks were so loud at points, that I could hear it clipping the line level somewhere in my chain (ticking sounds), sometimes in tune to the ripple of extreme low bass signals.
Though there is much articulation and rich synthesizer work for myriad robot-related sounds, the sound mix still had a strange sense, imo. It's like the soundscape was kept intentionally sparse, so that the many robot zings and boings have complete dominance. Bullet fire and artillery sounds were pleasingly detailed and dynamic, though. The weird part is when you hear all of these details, but then you see a collapsing building/structure that is seemingly absent from the sound. It's like all of the "mundane" ambient sound that should accompany all of the collateral destruction and damage you see on the screen have been seriously attenuated or muted right out. It's kind of a weird effect.
Strangely, I also noted instances where explosions and loud crashes were aggressively compressed and padded down (perhaps, to protect the precious ears of the kiddies?...just guessing). It's kind of like in that Indiana Jones movie where something happens that should have been deafeningly loud (figuratively) wasn't loud at all. It was no louder than the "medium" stuff that happened before it and after the event.
Then there is a weird layering of different sounds at different levels. It's like a perceptually "quiet" sound comes out perfectly clear right next to another sound that perceptually should utterly bury anything else short of a nuclear explosion. It's kind of hard to describe. It doesn't sound like a classic dynamic compression of a wide range soundtrack, but it is like the sound engineer took the individual sounds and purposely compiled them within a relatively narrow dynamic range. I don't want to poo-poo such a technique, because obviously it has merits and justifications for certain scenarios or to handle particular problems, but this incarnation of it just sounds a bit odd to me. Certainly, that is the realm of the sound-obsessive, though. The average person would never pick up on this as an "issue", rather just be pleased at how crisp, articulated, and windowed the soundtrack is. Nothing wrong with that. If it gives an enjoyable result, that would seem to be a successful objective. Many here seem satisfied with the TF2 soundtrack, so I would not beg to differ. It is definitely a high-performance audio work that really challenges the extremes of spectrum and dynamics.