I'm on Optus Yes Power. It has 20GB peak (noon to midnight) and 40GB off-peak (midnight to noon). Only download traffic is supposed to be counted in the calculations but I suspect they might "cheat" a little on this. There is no way the consumer can check on the ISP. Also, near the end of the calendar month the usage stats can jump wildly eg I have been caught out where I'm at say 98% peak usage and physically turn off the cable modem. After midnight (so now its off-peak) I switch back on and discover that I've been throttled to 64kbps as I have exceeded my peak usage. [They throttle to 64kbps if either peak or offpeak exceeds the limit]. Now this is impossible as I had no usage occurring. Hence the reason I say they "cheat" a little.

My son is with iiNet ADSL2+. He has 25GB peak and 40GB off-peak (I think this is 3am to 9am) with only downloads counted in the total. They only throttle the component where you exceed (ie, if he exceeds 25GB in peak then his offpeak is still at 20Mbps until he exceeds 40GB). He also has VOIP which he has never used but it gave him a better d/l allowance to pay the extra $10 a month. He always exceeds his 25/40 every month gotta love those torrents hey.

His ISP is very good as the plan started at 20/40 and they increased the peak to 25 free of charge. They also host quite a bit of data on their servers and these d/l are not counted in the limits.