Hi mate,
Not so sure about the leap of faith lol but I have started to support Ubuntu on the occasional call we get come in and then my mate turns up with an Ubuntu 8.04 system and an o2 dongle saying it wasnt working..... Great I thought kill two birds with one stone (help a mate and also help myself for any calls at work) I too have read most forums and took awhile for everything to sink in so here is what I did.
First off I upgraded the version of Ubuntu from 8.04 to 8.10 after connecting this new OS that I have come across to my home network by both ehternet and wifi just to make sure I could(there is nothing like learning lol).
I then followed these instructions to upgrade Ubunto fom 8.04 to 8.10 (I know you dont want to know this bit but after the ordeal I went through it's hopefully going to help others aswell so im posting my whole journey lol)
http://www.ubuntu.com/getubuntu/upgrading I waited hours for this to happen it installed and after reboot I was not shocked to find I had extra options in my System > Preferences > network configuration as I had read this version of 8.10 had a better network connection manager and drivers by default even though if you look a bit further they show up as the e220 or something like that but they are compatible.
I found I had a Mobile network tab and when selected I could see a defualt connection.
I also was shocked at this point I found out I had lost all connectivity via ethernet and wireless due to the upgrade but this was not a problem as I had a new lease of life to get this o2 dongle connected.
So I highlighted the default GSM connection 1 and clicked on edit.
after lots of forum reading and scratching of my head I got connected by these settings.
Number *99#
Username o2web (thats an o for oscar not a zero)
Password password
APN m-bb.o2.co.uk (thats an o for oscar not a zero)
and clicked Ok once I had entered the above details.
I then went to an icon on the panel that looks like two monitors with a triangle on the bottom right of them . (Network manager applet 0.70 it says under the about option after I right clicked on them to find out what the applet was called)
Anyway I left clicked on the icon and then left clicked on my GSM connection 1 which I had edited the details for previously and within 2-3 seconds I was connetced to the o2 network.
IDEAL!!!
(but with no credit no web pages will load apart from the top up page)
But now need to buy data access for this dongle
So I opened up firefox and went to URL
http://mobilebroadbandaccess.o2.co.uk and from here you can choose how much data you want to buy. Happy days.
Any way Sorry for the long story but it was a journey and if it can help you or any one at all then I am happy as I have now got it all off my chest and there is nothing like a bit of documentation.

Mission on lol now where more beer ?????