I've never experienced or heard of capping or throttling of connections in Korea, and as far as I can tell, there is no port blocking or detrimental traffic shaping going on.
Koreans do not use that much bittorrent, though edonkey was popular until a couple of years ago. I have heard some people being fined for distributing copyrighted material over p2p, but the fines are relatively moderate (a couple of thousand USD at most), and they don't cut you off.
Koreans get a most of their streaming content for free from commercial operators. Buying digital media online is also pretty cheap. I believe the current rate for non-DRM'd mp3 files is like 5 dollars for 40 songs.
This is of course killing DVD rental stores, as well as bootleggers (though they do sell Chinese bootlegged DVDs where there's more foreigners).
Currently I can saturate my 100mbps connection only when downloading stuff from the main portal sites or the larger universities (KAIST Gentoo mirrors are crazy fast), or downloading stuff from Korean peers on p2p networks.
They are pushing more and more stuff over the networks (HD and VOIP), though, so 100mbps can become a little too slow for a regular household in a couple of years.