It's enough to kill endgame torpedoes. Only targetable projectiles that can take a hit are that one Klingon special weapon and B'ger's giant plasma ball.
I actually used it for a while, even though it meant giving up a DPS console. I personally found I didn't need it that often and the point defense console was available often enough 90% of the time, and it's also useful in a lot of other situations. But the automated turret does have the benefit that it still has a good shot at saving you if you screw up. If you screw up with the point defense console, you're eating a torpedo.
It CAN hit B'ger's plasma ball, but it takes so much damage to destroy one its all but useless for it.
Personally I've not used the point defense thingy, but for me the ADT is wonderful.
It's really good at switching targets to incoming projectiles, and as far as I can remember, except for the Borg Death Ball, it takes out anything coming my way. I honestly don't know if i'd survive without it LOL (And I'm not joking)
I have both but I have been using the Point Defense System lately as it does more damage. But I don't like the cool down.
However, is the 45 plasma damage done by the ADT enough to take out torpedoes and incoming projectiles?
It's very good for taking out mines, heavy torpedoes and boarding party shuttles. It doesn't do enough damage to take out tricobalt devices, bio-neural warheads or the B'Ger one-shot plasma torpedoes. And it just can't intercept normal torpedoes at all.
Plus, does the ADT do a good job of making a judgment call stop shooting my primary target to take out an incoming projectile or boarding party?
Basically, it has a small cooldown between shots (about 3-4 seconds). If there's a projectile in range, it'll shoot that rather than a ship. The only problem is that there's usually multiple heavy plasma torpedoes from Romulan/Reman ships, and multiple shuttles from Boarding Party, so it can only take out one or two of them before they reach you.
Personally, I keep the ADT equipped on both my Cruiser and Science ships, specifically to deal with heavy torps and minefields while I concentrate on the main target. My Escorts do without, because I'd rather put more DPS boosting abilities into my Tac slots, so I'll usually toss the PDS into a spare Sci or Eng slot for those "oh crap" moments.