Build your home to your needs.....the open concept is a lovely idea, but only if it will work for your home culture....if you want the space decide how it will be used and build accordingly.

Do you mean a formal living room? (As in, two living rooms on the main.....the "formal" one being at the front of the house?)

We built our house last year and the floor plan we chose has a formal living room in addition to the fami.y room. We actually planned all along to use it as a formal dining room (our house is open with family room, informal dining, and kitchen in a row) as a short hallway connects it and our kitchen but after living here for almost a year (that room has been empty because we don't have enough furniture yet!), we're thinking we will make it a nice little sitting/reading room. My point is that it's basically a flexible room and if you have a room like that, you can change the function of it down the road so it functions in whatever way you need it to. It could be a second office space, dining room, library, living room, piano room, homeschooling room, etc.

Sure is nice to have it. We have converted ours to a library/sitting room. Love, love love it. Looks great, and is so comfortable to get away or when insomnia strikes, have a quiet place to go read and relax. Of course a comfortable chair and ottoman is a must! Good reading lamp, bookshelfs with some favorite books, and few accessories, maybe a little love seat for a guest. Works well. We are using 4 different chairs in ours right now, a small desk and a front window table for a lamp. Love it. Mainly, it just depends on what you want, need, or can afford! Think of the space as more of a "flex" space. That is a good way to think about it.