I don't have a mobile broadband but can answer some of your questions:
It does come with its own email accounts - you have to use hotmail, yahoo, googlemail and similar.
Googlemail does work very well with Thunderbird.
It is not compatible with these programs:
Alcohol 120 %
� Any DVD
� Camera Fix (WebCam software)
� Clone CD/Clone DVD
� Cyberlink Power DVD
� Daemon Tools
� Dell Media Direk Express
� DVD Shrink
� HP QuickPlay oder HP DVD Play
� HotSync Manager 6.01 (Komponente von Palm Desktop 4.1.4)
� Napster
� Nero Image Drive
� Norton Save and Restore
� Norton Ghost
� NTI CD/DVD Maker
� Pinnacle Instant CD/DVD Suite
� Pinnacle Media Suite
� Roxio Win on CD/Roxio CD Creator
� Unlead Filmbrennerei
Your firewall and avg should be fine.
As with any wireless internet access the data could be insecure, but if you are careful there should not be too much problem