As you probably recall I'm one of the diehards who uses a dial up
internet connection with 7.10.
I have been thinking of trying 8.10 but thought it would be best to
wait and see what the Ubuntu geniuses, such as yourself ;) had to say
about 8.10
I would be VERY interested to hear if you are making progress
configuring your modem cos I'm in the same boat as you.

You can always test dial up under 9.10 with a live CD.

My modem is an external USR 5686E model.

Since no Linux distribution includes a ling from /dev/modem to
/dev/ttyS0 or whatever channel the modem is installed you need to
create a symbolic link (as root) such as the following:
lrwxrwxrwx 1 root root 10 2008-11-09 08:26 /dev/modem -> /dev/ttyS0

I've found another way:

sudo pppconfig

will start a configuration utility that takes you through a setup
process for a PPP link. Then

sudo pon

and

sudo poff

will dial and drop a connection, respectively.

Setup was easier in the old Network Manager, though. In 7.10 and
8.04, I did it entirely from the GUI.

Too bad UBUNTU didn't keep the provision for dial-up that they had! I got it to
work in v8.04 thanks to help from this group but it still was still a pain so
went back to v6.06 which works great.