Starting with my connection at home...
I have BT Infinity, with a Draytek 2850n VDSL Modem Router. I run my own DHCP and DNS servers separately from the Draytek.
Prior to 7.1.1 I had spent a long time ensuring the WLAN channel I run on was clear of neighbours and others in the vicinity. I had got to a stage where the Wifi was fast, stable and strong.
Along comes 7.1.1, and that all goes out of the window. I carried out further testing, and moved my WLAN channel further up the range, as there were a couple more SSIDs in the area that were on similar channels.
I enabled 5GHz too, and that didnt help either... as the Draytek can only do 2.4 OR 5, I switched back to 2.4.
The signal strength is fine, but if you try and do a sustained transfer (ie. Youtube upload), it gets so far and bombs. I had it fail 3 out of 4 attempts. All the while, my iPad mini (1st Gen) running iOS 7.1 and Macbook (latest updates), remain connected. The logs in the router don't show a drop either.
My server, router and phone have all been reset - numerous times, the problem remains.
My wives i4 and iPad 2 are fine, but the phones on 7.1 still... (not sure about the iPad 2)
...and then my parents...
Who are also on BT Infinity, but use a HomeHub 5. The signal was stronger, but I was next to the hub. The connection however, was still as flakey. Switching back to 3G during heavy Wifi use. (Youtube upload).
...and then work...
I sit right below a Cisco Aironet, prior to 7.1.1, I had no issues. With the latest iOS, the connection is slow, and often becomes unresponsive and eventually drops back to 3G.
So...............