Let me start by saying that I don't usually log in to these forums unless there is something seriously good or bad about a product that I own or have used. In this case, I'm disturbed by the fact that a company as large as Apple has failed to respond to the many owners of their products who are experiencing similar issues, post IOS 8.x upgrade, with regards to WiFi performance. I'm a technical engineer with background in communication and network integration. This being said, I hope I can establish enough credentials to support the fact that Apple released this most current version of IOS with serious 802.11 issues.
My experience has been as follows: I've upgraded from IOS 7.1.2 to IOS 8.0.2 - four out of six of the IOS devices in our home. The two I did not upgrade are my wife's and she always (with caution) waits until bugs are worked out before upgrading. (A lesson I feel I should begin to follow after the most recent issues I've experienced with IOS 8.x.) Anyway, ALL of my upgraded devices (iPhone 5S and 3 iPads) have experienced issues with latency and connectivity to my local LAN (Asus RT-AC68U router), WiFi showing multiple bars on screen but apps saying no WiFi exists, and apps that are not yet compatible with the new IOS. The later is expected until developers catch up. The two devices (iPhone 5S and iPad) that were are still on IOS 7.1.2 have no issues.
The most interesting observation that points directly to IOS 8.x being the culprit is the fact that on occasion when I try to connect to my LAN resources, such as my security cameras or a NAS on our private network, I am unable to connect or ping those devices, even though IOS reports 3-4 bars of WiFi connectivity and my other non IOS 8.x have no problems with those network resources. When I turn off WiFi on the IOS 8.x device and use my AT&T GSM network, I can access all those devices fine. Both the private and public access require going thru my local router regardless so it is not a router issue. Again, all other non upgraded IOS and Windows devices on our network are not experiencing network issues. This points to the WiFi stack on the IOS 8.x devices as being the problem.
As with others posting in this forum, if you restart IOS or forget and rejoin the local network, this sometimes temporarily allows you connect to the WAN and local resources but even so, I've experiences anomalies such latency and poor network throughput. All this being said, Apple has an obligation to acknowledge this is an issue and as posted previously, give the consumer the confidence that they are at least working to correct the issue.
I've been a solid supporter of Apple and their products in the past, but it appears that Tim Cook and his team are falling short when it comes to what Steve Jobs founded this company on with regards to innovation and quality. I sincerely hope this post ends up on Mr. Cook's desk and Apple customers receive what is to be expected from a company they've been so loyal to in the past.