Just having someone around, who are working on a different piece of the same puzzle is a major motivator.
Though being able to go and watch the spitfire they rebuilt being demoed was really cool.
http://c2.com/cgi/wiki?PeoplewareOnSharedSpaces
"enclosed offices need not be one-person offices. The two- or three- or four-person office makes a lot more sense, particularly if office groupings can be made to align with work groups. Even in open-plan offices, co-workers should be encouraged to modify the grid to put their areas together into small suites. When this is allowed, people become positively ingenious in laying out the area to serve all their needs: work space, meeting space, and social space. Since they tend to be in interaction mode together or simultaneously in flow mode, they have less noise clash with each other than they would with randomly selected neighbors."
I always found it very easy to concentrate in big spaces as long as I feel nobody cares about what I am doing, and that seems easy in a big room. I also don't care much about small distractions or noises, I always hear people complaining about getting out of the zone when they have to chat a bit with a coworker. It takes me a big effort to get into the zone when I am starting to work, some kind of a starting period while I load all the relevant information in my head, but once I'm there I can get in and out and attend subtasks or have a conversation with somebody with no problem.
At home, I can find ANYTHING to entertain me.
At work, when I have a group of motivated peers around me who are focused on the same goal, so am I.
But as said elsewhere, that doesn't mean open offices are the answer.