Well I did some extensive testing today. Spent the whole day on the trial account, and started up an NNTP download and let it run for a minute to get up to full speed every hour on the hour.
Got full speed all morning and early afternoon, until around 2pm when it started degrading steadily. By 4pm I was only managing around 1.1MB/sec and it's gone up and down since then. As I type this, after hours, I still cannot exceed 1.3MB/sec, when max speed should be 2.0MB/sec. Before anyone jumps in with "it's your exchange!", if I switch across to my Axxess account I get line speed.
I even went so far as to buy an account with the same news provider as Orihalcon and duplicate his server/port setup, with much the same results. I can only conclude that either WA hates me, or NNTP is pretty heavily shaped during the day, or WA are having the same IPC capacity issues in the South as Afrihost are currently experiencing. Granted, this is a lot better than the 120k/sec which was my maximum speed during the day on WA a few months ago when I was still with them, but not ideal. If I could be assured of >1MB/sec performance during office hours I might actually consider moving back, but since I don't know what the cause of the slowdown is, I don't want to sign up again and have the service degrade further.