Hi-
Just wanted to add my 2 cents. I'm not disagreeing with chooks4life at all, but I do have water in my coop and wanted to share my reasons why.
I'm in the south and dealing with extreme heat, and I have water in both the coop and run. Even though the run is shaded, the run water evaporates much faster than the coop. I'm still using the waterers from TSC (not nipple waterers), so I think of the coop as my "backup" water source. If the one in the run gets tipped over, goes dry, or gets dirty, then I have another water source in the coop. At the worst part of the day they do like to hang out in the coop and that waterer does get used (so it isn't wasted real estate for me).
I also want water in the coop because I've found that if I keep food and water in there then they are much less stressed in the morning if I'm not out there at dawn to open the door. I'm the only "automatic" door opener and sometimes I'm not so automatic, lol! With food and water in the coop they just mill around peacefully until I get there, but without it they get stressed and start fighting.
I think it's just a personal preference. Most people don't put food & water in the coop, but it works for me.