So, there's something odd about H2A campaign. There's been several instances where I could sneak up on enemies in the original, but now they know I'm there even before I've started moving. Most recent thing I can think of is the big grav lift on Gravemind. I usually go down and smack the Brute on guard in the back of the head, but now the guy just turns around and attacks the moment I touch down.
Maybe it's just coincidence, but I thought it was weird.
Another thing is dialogue. Stuff characters used to say on the radio, e.g. Miranda, Johnson and Guilty Spark during the fight with Tartarus, now aren't. You can vaguely hear them talking in the distance while fighting. This happens a lot during the game, was kind of a downer.
Last thing that bugged me was the final cutscene. "Sir, finishing this fight". Cut to black, wait a few seconds to load, and then they let the music play. :lol So weird.