I agree. Mine has also become worse since the firmware update I installed earlier today. After a few restarts it does seem to be holding stable - it dropped out frequently to begin with - but I have to disable my USB GB Ethernet Adapter and Bluetooth PAN
to get max speed of 144.0 Mbps on 2.4Ghz (I have a router capable of 5Ghz but I'll settle for getting this sorted first). Although sometimes it hovers around 1.0-5.5 Mbps even with these disabled!
I appreciate the need to save power but not at the expense of it functioning at all. What's frustrating is not having any control over how the adapter performs. I would hazard a guess that it all derives from Connected Standby and it's half-baked implementation
on the Haswell CPU's /64 Bit OS. I only hope Microsoft can fix it without using us all as guinea pigs.