Aye, the engine is showing its age. Some new effects look to be in place when the bridge blows, but otherwise it looks like Halo 3's engine. Looks good, but by this fall especially it will be dated a bit.
The game really is aimed at the hardcore Halo player. What does everyone bitch about missing from Halo 1? The pistol. It's back. What does everyone bitch about Halo 2? That the infamous E3 2003 demo of open urban combat at night that got scrapped. Now that's in. And I'm guessing most Halo players couldn't pick an ODST out of a lineup, but the hardcore know them well. And everyone complained about the story tell in in Halo 3; that's gotten an overhaul with a new approach. The game is being made by a crew of the Bungie old timers like Staten, and it shows.
It won't appeal to everyone. But to the Halo audience it's aimed at, holy jebus.