Open office concept is about a way of arranging your internal environment (lay out) of your office. This concept removes all cubicles form office and forces all staff members to work in a common open office layout. Since all creatures are territorial you need to assign a permanent seat (place) for each staff member. Some offices have even gone against this principal also and assigns no specific places to you. You can come and sit any where you want or you can work from home even.
However I find it is comfortable and make it personal to sit in a specific place. This environment allows you to get up and go to a colleague and discuss if you have a problem or any thing, to discuss briefly, rather than fixing a meeting and delaying your actions. It is mostly good for organizations which need to discuss small matters all the time. Whenever I have to sort out a technical matter, I just get up and go to Sanjaya. We do not have bells as in govt offices. So you cannot summon people; you have to go to them regardless of your seniority.
Since my PA is sitting next to me in an exactly similar table, this removes the disparity in office. Everybody has similar chairs and tables. (In govt the boss has the best table and chair:)
Since my PA is sitting next to me I can ask her to attend to urgent matters rather than calling her and assigning work. Work assignment is happening continuously.
Monitoring/supervision is also very easy in open office layout as you can see all the people. Our boss is sitting in 2nd floor at a table from which he can see almost all movements. There was a time at ICTA that if you leave office at 5.30 pm the boss would ask, Wasantha are you on a half day today?

So he is sure to sit aat his table at 8-9 am and 5-6 pm to note when people come and go.
I am sitting in the same position in 3rd floor so I can observe all activities in the office (only if I am in office; my problem is that I am always in other government offices having meetings

Open Office layout also increases the efficiency of using equipment. For about 30 people in our floor we have only 2 printers. One for all and one for my PA (for urgent work as sometimes people print over 250 copies; so you have to wait). The common printer works as the scanner, copier and printer. All have to walk up to the printer which has been positioned in a central place.
Negative side is that somebody can come and discuss an issue with your neighbor and continue to be noisy. At such times it can disturb others, speacilly who are sitting close to you; In such occasions people in my office would shout and say pls go to a meeting room. So if you are going for an open office layout you need to have ample meeting rooms. Since Thushara is sitting in front of me, he gets disturbed all the time as a lot of people come to discuss matters with me. So I try to get up and go to a meeting room at such occasions.
Open office also inculcates a friendly office culture. Whenever Thusahra or my PA (Chathurani) is eating biscuits or something for tea (when you work long hours you always get hungry all the time) I am also offered same snacks by them over the half wall. We also pass work, docs, thumb drives etc over the half wall , not only food.
In an open office you cannot keep your table untidy as everybody can see it. Some stick to clean desk policy where you cannot leave any dos on your desk when you go home. Open office promotes clean desk policy as you cannot leave important docs on your table.
So these are the pluses and minuses of open office from my point of view. See I can see it all:)