This more an observation that the rules are unclear on the matter than an actual question. The description of Overwatch states how it is activated, as well as stating that it ends if the character performs other actions/reactions. But it does not explicitly state that Overwatch ends after the attack is made.

I didn't catch this because I was familiar with the old system. Looking at it now, it shouldn't take a rules lawyer to determine that allowing a character to make an attack action falls under the "any actions or reaction (other than free actions)" statement, thus ending Overwatch.

Comparing this to DH1, it appears that during the adaptation of the material, the paragraph detailing DH1s mechanic of putting an upper time limit on Overwatch (probably the least used rule in DH1 - I can see why they pulled it out) was removed. This paragraph contained DH1s clarification on this matter: "Once you have used your Full Auto Burst Action, Overwatch ends."

On Overwatch in general, its interesting/odd to see that the max range was removed from the action. I'm not certain this is a good idea, but at the same time I seriously doubt it would ever come up anyway. Its interesting to see the removal of high RoF from the attack (i.e. you can now Overwatch with a single shot weapon), I don't think this will have any negative effects.

It would be nice to see better clarification of that second to last paragraph. What defines "at the same time as another character's action"? Another Overwatch? An Overwatch action that triggers midway through anothers move action?

If I have an Overwatch action up on the doorway, and someone mid-movement action walks through (thus setting off my trigger) what happens?

Is it:

A: Its an action at the same time, thus compare Agility. If the shooter wins, shoot at a point interrupting the movement, if shooterfails, moving character can act as they see fit. If so, should they be able to move to avoid the incoming fire? What if they can't see the shooter (thus no visual, and they haven't been shot at yet)?

B: Since the move action is already underway, it doesn't compete, thus a shot made immediately?

C: Interrupting action's are not possible anyway, so the shot is made when the movement is completed.

I think even though it reads otherwise, this has to be interpreted as the Overwatch ending after the first time an attack is made.

This would actually work fine as is, if the Overwatch action type was Utility rather than Attack. In that case, the Ranged Attack it allows you to make would be the one Attack action that is allowable per turn and it would be covered by the other rules. However, as it is an Attack action itself already, technically, Overwatch shouldn't even be usable as you spend an Attack action to set it up and then you need to use an Attack action when you fire.

What I would actually really like to see, would be Overwatch be a Utility action so that you could fire and then go onto Overwatch with remaining AP. But I don't think they'll do that.