Here in Sweden I have been using 3 mobile wide band for 2 years both
with Ubuntu 8.10 and now 9.4. No problems at all and fast enough for me
- cut my old ADSL costs in half!

I sometimes use a UK Vodafone mobile connect PCMCIA card, and got the driver
from here:
https://forge.betavine.net/
You will see there are USB drivers here too.

I used the provider called 3, for 4 months in both Linux and Dos and got
the feeling that Linux was better and faster. Average download speeds
was 40Kb in evening with 6Kb at peak times. Mobile broadband is very
expensive from all providers. It did however serve a purpose for me.
There were no setup problems at all with Linux it was a simple plug in,
choose an option and everything worked.

I used 3 for 4 months in Linux and Dos and got the feeling that Linux
was better and faster. Average download speeds was 40Kb in evening with
6Kb at peak times. Mobile broadband is very expensive overall the
providers. It did however serve a purpose for me.
There were no setup problems at all with Linux it was a simple plug in,
choose an option and everything worked.

I have been using a mobile USB dongle since 8.04 with no complaints. I would
recommend having at least 8.10 or above though as the network manager is much
better working with them. Basically you plug it in, a wizard should start up and
you just tell it which country you are in, pick your network provider from the
list and you are on the internet. Simple!

I can not see you have any problems unless you are running pre 8.04 version of
Ubuntu, then you have to write a wvdial file to use the dongle. If you are fully
up-to-date though then do not hesitate. Just google the make/model of dongle
they are offering with your version of Ubuntu and you should know straight away
if there has ever been an issue.

beware
some mobile broadband contracts give you cheap internet
up to a certain limit then charge huge amounts per 100MB after that,
many people use it for several months
then download a lot of videos andor bbc iplayer
and get bills in hundreds if not thousands of pounds!

Now I know that it should work, I'll
investigate further to find a service that suits my needs.

My experience of them with MS is poor, they are weak signals and are
often hard to detect in the South of England.