World interaction is no doubt good but movement will always need to be somewhat sluggish and inertia-ridden otherwise the gameplay will not be like Red Orchestra.
People cannot move around gracefully or stop on a dime when trodding around blown-out urban landscapes covered in loose brick and rubble, and RO needs to represent that or else the combat will be too fast paced and stilted.
From what I've seen of the trailers, the third person animations seem to have a lot of inertia to them, so hopefully that will translate equally to the actual player movements.
HoS still has the inertia (look at Ramm playing, not the bots, the bots haven't had the inertia added yet, they where having problems with it breaking their pathfinding, so that's still beeing worked on last we heard, and was not done yet for the PAX and Igromir vids, at that time it was only in place for human players), and you are still confined to what a human could do, none of that looks to have changed in the slightest, and the guns are still as deadly (if not more so, recoil tweaks for the win).
What is changing, is that you can do realistic things, like cancel a reload and try to use a melee attack instead if you need to, and that you can start sprinting before the "lower gun to hip" anim is done playing, so like a real person, you could try to run for your life if a grenade lands next to you, and automatically put down the gun as you start doing so, instead of standing there like a statue patiently waiting to lower your gun first for some arbitrary and unrealistic reason.
It's fine details, and it wont drastically change how the game is played, what made RO's gameplay was the combination of deadly and accurate guns, and realistic player movement, and that will still be the order of the day in HoS, it will just come without the side order of frustration that comes with fighting stiff controls.
Will it change things slighty? I sure hope so! Because Ost, whilst damned good, was not perfect, and i hope HoS will up the ante.
EDIT: To add to the above, a lot of what we're seeing gun and movement wise in HoS, really reminds me of how things where in the mod days (you know, aside from the brand new stuff), i don't know if you where playing RO back then, not everyone here did, but some important differences was that SMG's had less recoil, some of the anims could be overwritten in earlier builds (it looked terrible, but played much nicer), and there wasen't as big a need to lie prone or rest guns on stuff just to reasonably control the weapons.
And none of that made the mod any less tactical, none of it caused the problems you fear it might, it actually worked really well, and a lot of us never did like some of the changes that made it into Ost, the mod was better in some ways, Ost better in others, and i can't help feeling that HoS looks like the best of them both, with some new stuff tossed in for good measure.