During the skirmishes with the poachers, and later with British and American soldiers, we discovered that combat has evolved beyond what it was in Assassin's Creed 2 and its spin-offs.
In our demo, Connor had a sword, a pistol, the Assassins' hidden blades, and his signature tomahawk, not to mention expendable items like trip mines (seriously a blast), rope darts, arrows, smoke bombs, and more.
Slashing wantonly by jamming the "X" button won't be nearly as effective as it has been in the past, and countering enemies' attacks will be key. Once an enemy has been countered, time slows and different buttons will accomplish different actions—"B" throws an enemy, "X" kills, and "Y" uses whatever secondary item you've got out (pistol, trip mine, snare, etc.).
It was extra fun to stick an enemy with a trip mine and chuck him away, or whip out Connor's pistol lightning quick and fire off a shot in the middle of a fight. But even countering didn't always work, and some heavy enemies required even more thoughtful strategies. Overall we love the ways combat has evolved.