And best of all, you can get extra health and give it to teammates who are hurting in the style of NPC medics (ammo too, though I’ve rarely had to go there).
If somebody passes through a scripted area like an elevator or something, even if it’s not immediate, everybody does get teleported ahead to meet each other.
When one player is given a new weapon, everyone is given it automatically. Each player is represented by their Steam icon floating over their head, which is used as a sort of radar in essence, allowing you to keep tabs on where everybody is at any given time. As I said earlier, the Synergy interface does very little to interfere with the actual gameplay mechanics, only improving upon certain facets to make co-op more viable. I recently played through all of Half-Life 2 with a friend of mine, and the gameplay is actually phenomenally more fun than it is with just one player.