...same as with major roads, train lines, power lines, power plants (including but not limited to nuclear and wind), affordable (i.e. high density) housing etc. etc.
US experience is different, with big diesels and primarily freight. I'd rate them as similarly annoying to a divided highway, but I suppose it depends on the region and the specifics
(The navy blue trains with yellow 'noses' are high-speed commuter trains, the dark blue, gold and white ones are the high-speed trains to France, the plain white ones are normal-speed commuter trains to London.)
I think the continuously welded rails are the biggest improvement, as they remove most of the "clackety-clack". Instead you get the "hiss", but that's only noticeable from really close.
