An isolated case of being difficult to close the action, not able to get enough repeated uses from the holder, minor isolated stuff refuted by others. The sights might have been problematic on another rifle.
Every single gun produced is different and unique. Most have claimed that they are a good U.S. made model for the price.
Yes, I think the discs help to weatherized although the action is already closed, but they may more importantly help keep some powder residue from entering into the trigger mechanism and receiver area of the gun.
A Pain? Not if they are preloaded so that you can just pop one in and out. But you have to realize that loading and shooting plastic sabots with bullets is a pain all by itself. They don't load as easily as patched round balls or shooting plain lead conical bullets. So, those disc things can't be as much of a pain as loading those, they're supposed to make it easier to handle the 209 primers. Just buy some extras.
One thing that I do look for when buying an inline though, is whether there is a quick to use safety or not. I'd rather not have to cock the hammer when a deer is within range, while the safety on another model can be quickly flicked off and shooting can proceed. Do you know whether or not the H&R has a quick flip type safety? That's something to consider, and if the stock is wood, it may be a little heavier with the scope & long barrel, depending on the method of hunting.