iinet, as i understand it, slows down to a CRAWL at the stroke of midnight, where the "bliink time" kicks in. (off peak usage, with guys on the 6GB/6GB plan leeching etc and queueing their download managers to start).
the best adsl deal atm, IMO, would be ozforces or something like netspace.
i'm on telstra cable now, have been for the past 5 years. i used to download a lot of "things" (wink wink nudge nudge) -- however with the 3GB cap, there's not much I can do. what with a handful of computers all sharing the same connection at home, you'd be lucky if you could stay on IRC all day.
back on topic though,
the only positive thing i could say about telstra is their bandwidth.
the speeds are great on cable (max of 1MB/s, averages ~600-700KB/s from within telstra's gamearena and files.bigpond.com)
look around, read all you can about gisps (gaming isps) or the normal isp and choose the best deal for you. some prefer fast downloads whenever they want, some prefer slow downloads but with a larger quota (limit), etc.