So my neighbor asked me to come over and help him out with a home plan that he has been thinking of building. They just built a house a couple of years ago, but I guess they are gluttons for punishment. They are looking at another lot up the hill and are starting over. We took a ride across town to a home he liked. It had some great curb appeal, and you could tell the home owner [who had the home custom designed] had really thought things through. Turns out the homeowner is related to a well known interior designer in the area. You can really tell when a home is well thought out. I have been in homes that are around 1400-1500 sq. ft. that feel like they are 1800 sq. ft. just because of the way they are planned. Its really important to take time when designing a new home and think things through. This is why stock house plans are a great deal. Designers deal with home plan layouts every day. I promise they have learned things through their experience that most people don't know, that can greatly affect the functionality of a plan, and often times the cost.
For example, great rooms are generally the place that everyone wants to hang out in the home. If you put a fireplace on one wall, entertainment center on the other, border the kitchen on the other and have entrances to bedroooms on the forth wall, you'll have minimal wall space for couches and chairs, which can hamper the functionality of that room. a 12x12 room can be more functional than a 16x16 room if the layout is poor. If you take the time to really think through your floor plan, you can have a very functional floor plan that is comfortable to live in and regardless of what some think... functional can be very aesthetically pleasing if done right. Not trying to put a plug in for home designers here... but with an experienced professional helping you out, you're likely to get a much better end product. Which I feel is very important, a home is a large investment; you may as well make it the best it can be within your budget.