I just picked up the HVR a few days ago and I have been using for most of those days. I will real quickly go over its pros and cons as well as how I think it should be used.
-Highest damage per a shot(2 shot kill even with hp upgrades)
-Must be reloaded before switching weapons
-Slows movement speed when equipped
-Poor at taking out enemies by itself due to slow reload speed
-Can be negated for the most part if the enemy uses cover
Usage: I feel the HVR works best at simply applying pressure on your enemies since its rate of fire is very low and struggles at killing enemies in cover. What it really shines at is getting assists. You put one shot into someone and then your teammates can rush the cover they use and take them out with two bullets from an OCA or one from a N-tec. This makes the other team operate slowly and less aggressively due to how easy it is to gank someone who has been hit by the HVR. Since most objectives are based on time, the HVR can really make a difference if used to simply slow the enemies down and not necessarily to kill them. The user should not just focus on one enemy in order to get a kill, but should try to spread the damage out to the entire enemy team to apply pressure.
Just as an example of this, Gong and I were playing a time based mission one day. He had the HVR while I carried the OCA. What happened was that we got to the objective first and had time to setup a position with Gong on a highpoint while I covered the ground. The enemies simply were not willing to rush across the street since whenever they ran out Gong would shoot them and I would rush over to scare them off. We were able to win the match simply because the other team couldn't act aggressively in order to take the checkpoint because of the pressure put on them by the HVR and the time limit ran out.
People should realize when picking up the HVR that their job is not killing enemies, but applying pressure to slow them down and give your teammates a much easier fight. The HVR simply excels at getting assists, slowing down enemies, and stealing your teammates' kills. I just want people to realize that stealing kills is not your primary job and that spreading the damage to enemies is actually the most effective way to use the HVR.
As always comment and tell me what you think :)