I have one and am always doing research to make improvement.
First it does get hot inside during the summer, so u will want to have planty of ventilation, I have cut vents near the top of the walls and I leave the door open during the summer and let the ladies run free. next summer i am going to build a lattice and plant some honey suckle on the south side hoping to reduce the suns impact as well.
as for winter... this will be my first winter but from what I have read its condensation on the metal/aluminum walls that will be a problem, so i am going to "line" the inside of my walls with plywood. my shed was also guilt on a cement slab in the 70s and the seal isnt great so during heavy rains (which are few and far between here in Idaho) i have to watch and make sure the bottom dries out, for the winter i am adding pallets on the ground to raise the ladies up from the moisture, I'll put *food grade* DE down as well to help with this in case. then a layer of old lanolium then use the deep litter method of pine shavings on top.
rain noise is also a factor with metal/aluminum sheds if the roof is also metal. I have seen some "living roofs" on here and I am toying with this idea for added coolness in the summer and to protect their ears from the rain noise (they have gone outside and sat in the rain as opposed to staying inside and dry, so i know it bothers them.)
if you have any other questions go ahead and PM me, I am always tryign to think of new ways to freecycle stuff and make my old metal shed a better coop for the ladies.
-Heidi