I'm on IS using a 4mb connection. I don't know what IS are doing but I can't download faster than on average 50kb/s per file from rapidshare and I'm battling to exceed 300kb/s in total, I've got 8 files downloading at a time. I'm normally able to average 430kb/s from rapidshare with 5 files at a time.
I've tested some files from other sites and I get my full line speed. I sure hope IS isn't shaping rapidshare downloads.