The first rifle I ever built, years ago, has a straight barrel, a 19th century development. It is 50 caliber, and feels like I am swinging a 42" anvil around. All subsequent guns I have done have been swamped 44", 45 calibers, and they are a dream to point by comparison. The balance is spot-on, and they feel very natural, like an extension of your arm. It amazes me still how much difference in feel there is.
But the reason I started using swamped barrels is that they were historically correct. And yes, when sighting down the barrel, the taper and flare seem quite pronounced. A swamped barrel has the disadvantage of being quite a bit more work to inlet correctly, but I think it is worth it for the perfect balance you can achieve with it. However, once the barrel is inletted, it dictates the angle of the side plate and lock mouldings, which I find add to the aesthetic appeal of the guns made with swamped barrels. I know it is a subtle detail, but it is there in the ancient originals too.
If you get a chance, go hold a well made rifle with a swamped barrel and compare it to a straight barrel... It is a joy to point and shoot.
Matt