I commute 160km per day on a 1150GS...
It's now at 60k km and still running beatifully.
It's just about reaching the end of its running in period!
Personally, I love commuting on the GS - high, upright position and huge road presence compared to most bikes. It's not a narrow bike, though, and it's f***ing heavy, which makes filtering more difficult if you have to do that. It's surprisingly fun in the twisty stuff on the way home, too.
Having said that, when I lived in London I commuted from one side to the other on a 28 year old Guzzi V50, which was about perfect as a commuter. Nimble, enough grunt to cope easily with motorways and medium length journeys, totally overlooked by thieves, laughably cheap insurance (I think it was £86 fully comp with full European cover). Of course, being a Guzzi you need to be able to do some light spannering...
HTH - Adam...