When you first start the distribution upgrade process it warns you that the download process will take <n> time over a modem and <n> time over a 1Mbit DSL line. This is a) all told as a big block of text and b) the scarily large <n> value (> 1 day, IIRC) for a modem is listed first. It's very easy to glance at this and misparse it. It'd be nice if the smaller (DSL) time could be listed first, and even better IMO if they were listed as a table.
Also, the download time for my 2Mbit ADSL was something like 2 hours. Apparently if I'd been on a modem, it would have been a day. Before it starts the process, the dist upgrader asks you to close all other open applications and says that the process can't be interrupted once it's begun. Both of these would seem to apply to the upgrade, not the download of packages to upgrade. I think it'd be much more friendly if the "Stop what you're doing & no going back from here" warnings didn't kick in until the download was complete and the upgrade was ready to begin.
Thanks for your bugreport.
Ack for both issues.