I just finished mine - it is a 12 x 20 foot enclosed run (tin roof with insulation) with an enclosure on one end (ramps leading up to the enclosure) for the chickens to hang out on cold days. The house enclosure has 10 nest boxes accessible from the outside for egg gathering. I used 1 sq centimeter hardware cloth for my pen (we have HUGE chicken snakes here in TX) and the insulation under the roof keeps it about 10-15 degrees cooler for the birds. I buried the hardware cloth down about 6 inches and added treated lumber around the edges to keep the sand inside which is what I use for their flooring. I have 15 chickens in it.
I have some VERY huge stumps from old trees that I rolled into their pen (with lots of effort and some blood - LOL!) that make great perches and seats for visitors (I like to interact with my birds daily). I installed roosts out of natural tree branches and feeders made from PVC pipe for their pelleted feed and oyster shell, and I'm still looking for the perfect auto waterer to install in the corner.
Sand flooring is a life saver. Since I use feed pans as my temporary waterers, I can just dump them out right there in the pen and it soaks down almost instantly so the run never stays wet for long periods of time and it works great for spraying things down when things get dusty. PLUS, chicken poop dries up very quickly and it is so easy to clean out with a manure fork. Keep the work simple, I say, so you can enjoy it more.
I asked hubby to build me something that would last 20 years and would compliment our ranch and other buildings and he did a **** fine job. I have my coop sitting right in the middle back area of my garden and I'm very pleased. It is right next to water and electric and the chickens get all the wonderful pickings from my garden - they go crazy for squash!
They will also have a yard area where they can free range from time to time (as soon as we replace some of the fencing we tore down in order to build the coop) that will be about 80 x 80 with 5 foot tall rolled sheep wire. They will still jump the fence, but they always come back. I'm going to decorate it with all of the usual fun stuff - signs, flower beds in front, etc but it is already a 100 degrees here in TX so I'm not in a hurry to get out there and do the flowerbeds right now although I have all of these flowering plants (that are already flowering) that I ordered from Gurneys this past spring that are waiting to go into my flower bed. They are a collection of butterfly/hummingbird attracting shrubs that will grow about 4 foot tall and provide wind block and shade as well.
I got the idea for mine from a post on the run design forum, and then I just tweaked it a little and hubby made my thought into a reality. Cost wasn't of any issue, so we went the extra mile to make it last a lifetime. It's so nice in fact, I think my mother in law would probably be quite comfortable staying in it when she visits.
Overall we spent about 8 weekends working on it and about $3500 at Lowes (and that was with discounts and contractor pricing).
No matter the size, shape or budget - don't cut corners - build it solid and use good materials. If I ever get tired of chickens (I doubt it) then my run can be used for anything from rabbits to peacocks to - did I already mention my mother in law? Anyway, we built it multi-purpose on purpose. So that might be something else to consider - especially if you put alot of $ into it.
Have fun!