Today, as an experiment, I attempted to fix a Debian bug while on the train to work.
I use a 3G card from Three.co.uk in my Lenovo Thinkpad x121e, and my commute is from Southampton Central to Fleet (changing at Winchester) - just under an hour. 3G coverage is not 100%, but tends to be better around the major stops.
First, I found a bug. I used udd.debian.org to browse for a relatively simple RC bug, and found bug #674992 in actionaz.