I upgraded a couple of days ago... from 384 line to 4meg line same situation as you and yeah its true! you should get about 430KB/s!
but... (there is a but!) it depends so much on where you download from (more than i thought) for instance a torrent download only gives me about 100KB/s, thats also because of telkom shaping the cr@p out of torrents, however, having said that, when downloading from international servers, expect it to be slower!
nice just imagine thats still slow to international requirements...i wonder how it would be when he have superfast internet like in japan and korea...