I enjoyed the swing in mood, but essentially it's just more Halo 3 with a hub level and more formulaic individual mission design. There's a warthog mission, a tank mission, a sniper level, a sewer level etc; it's not gonna be surprising on this front. The changes in mechanics and game feel are also pretty miniscule despite you playing as weaker ODST soldiers rather than herculean Chief.

It's still solid and worth going through, especially as a sneak peak for how well halo combat could work in a free to roam interconnected map when player is left to progress at their own pace. I'd be pretty pissed if it was sold to me as a full-price game tho.