So I've played over 30 matches so far in plat with my boy(I know it's not high elo or anything) and I have a few thoughts about him which are probably wrong but that's fine. I haven't seen anyone else playing Harbor pretty much at all, and for the most part the general consensus in most of my games is people perceive him to be really weak. I think he may be a bit weak as a standard controller, but I think his main strength is very notable and gives him a decent advantage over other agents. Theses are my thoughts on what he sort of brings/doesn't bring to the fight after playing some solo queue and 5 man stacks for comp.

Strengths:

• Versatility - This is by far his best strength and a lot of the value Harbor gets is (obviously as a controller) staying alive, playing for retake, and being able to wall off where the enemy is playing. He's insanely good on retake if you have a sova or any initiator that can find out where people are playing (if you don't have ult) you can make your team's job so much easier. Because he can bend his wall, it lasts a long ass time, and he can do it far away, he can be useful in any situation.
• Retakes - If you save your wave and cove abilities for retake you can literally make the bomb site look like Atlantis with the amount of water and site you block if you want. He's just really good at this. Also his ult is incredibly strong for retakes since you can pinpoint where people are playing by seeing where the geysers are pumping, and then wall them off and push on site.
• Pistol round bomb planting - With cove you're pretty much guaranteed to get the bomb planted, you just throw your dome down and go plant. Just make sure you have someone covering you inside the dome because people usually run through to snipe you.

Weaknesses:

• Defending against rushes - He's got walls and can block line of site but he doesn't have anything to STOP people from pushing him hard like an omen blind, a brim/viper molly, astra displacement, etc. It can be a really big issue since if you're the only controller your team is sort of going to be relying on you to be able to at least defend the site you're on/drastically slow down their push.
• Anchoring - Because of the aforementioned weakness he's not a great anchor. Which isn't great if you're playing a controller and you don't have a killjoy, cypher, etc. You're best to play far back on site try to get a pick if they peek through your util and play for re-take.
• Teammates don't play around you (yet) - This may be because he's a newer agent, but I'll often find my team not waiting for my wall to come back for re-take and they just run in and die. Which to say the least, is very frustrating.
• You may need another controller or an anchor - You may find on some maps like Haven he's not the greatest and you might need a sentinel or another controller to cover B/A to slow down fast rushes. On a map like Haven or Ascent people are going to just flash through your util and get on site because you have no molly or blind etc.

TL;DR he's versatile and good at retakes, but he's not super strong on defense, stopping rushes, and anchoring.