It didn't really help that the stream was having issues during the Halo 5 segment. Regardless, it looked almost exactly like Halo 4? I am going to have to reserve my judgment for when they release it in true quality, but still.
Dunno, I am a massive massive Halo fan, but it went by so quickly. I just find it hard to grasp that that little segment was 'all there is'.
I also agree with the former posters. The previews said that the levels are gigantic and that they have gone back to the more classic Halo open level design. Then they show a very linear and cinematic segment at the conference? Maybe that's why it reminded me of Halo 4..