I average three days a week on the road, and also carry an iPad with me. I think the combination of the two is just perfect for what I need. Most media consumption is done on the iPad, and a fair bit of email reading, along with short responses.
The MBA 11 is perfect for all of the extended writing, form filling, equipment configuring etc. I have it configured with BootCamp, as most of my equipment configuration software is Windows based.
I would not want to give up my office system, which is a MBP 15 driving three monitors, maxed out on Ram and sporting a 256 GB SSD, but the MBA 11 picks up the slack nicely while on the road. Drop Box keeps all the important stuff in sync, and I also have a Raid 5 FTP server sitting in the office that I can get to easily from the MBA or iPad.