I am having very inconsistent issues as well, and I am very confident that it is software related. My most notable and confusing problems are from my Family Room AppleTV and my iPad, which both have the latest version of iOS. None of these problems existed before the recent iOS updates. I also have 2 other AppleTVs that seem to be working fine, hence the inconsistency comment.
1) AppleTV - I am losing home sharing often, seemingly once the AppleTV wakes from sleep, but I have yet to confirm the timing. I have tried restarting iTunes on my iMac, and that solves the problem. I have also tried just rebooting the router without touching iTunes, and I believe that worked (I say I believe it worked because I tried so many things I cant remember for sure).
2) iPad - I get stutters that cause me to lose internet connectivity while still showing as being on wifi, sometimes for a few seconds, sometimes for many minutes. In the Airport app, I seem to lose connectivity to the routers but sometimes can still access the Internet. Thats actually the main reason I think it is software related.
I have 3 routers in my house, the main Time Capsule and 2 Airport Expresses that extend wifi range. Also, 1 of the Airport Express units is connected to a switch which then feeds 7 other devices via ethernet.
I really dont want to go out to the Apple Store with the router, only to be sent home with it, which is my guess as to what will happen. I understand that iOS 8.1 should be out in the next few weeks, along with the OSX Yosemite operating system. I hope that fixes the problem. If not, then I will figure out how to change out the router (which is still under warranty).
I really really doubt this is hardware, again all functioned perfectly before the iOS updates.