I thought I was going mad!
It's not limited to iOS8 for me, it started when I upgraded to a BT Home Hub 5 which has 2.4gHz and 5gHz
Currenntly running:
iMac 27" Late 2012 - Mavericks
MacBook Air Mid 2012 - Yosemite Beta 5
iPhone 5 - iOS 8.0.2
iPad Mini (Retina) - iOS 8.0.2
iPad 3 (Retina) - iOS 8.0.2
Up to a couple of weeks ago, I'd get a glitch where I could see the network but was stuck in the log in loop. Constantly asking for password, on all devices, but not at the same time.
Problem resolved by restarting the router.
Since the upgrades to iOS 8, and 8.0.2, I don't get the log in loop any more - which used to alert me to a problem - now I just get drop-outs. Face time calls will bomb out, I'll get pages not loading as not connected to the internet, even though Wi-Fi is at full strength.
I use RowMote Helper/Pro for pure laziness, and the last week or so, the iOS devices connect to the BigMac sporadically, and I've had to actually get up to pause shows! (The horror!)
I've just gone into the router and manually switched off the 5gHz frequency, and since running on 2.4gHz, it's been much more stable - no bomb outs yet.