Some feedback for Intel:
The 15.6.1 and earlier drivers seem to care greatly about what access point they're connecting to.
I've got a Samsung NP540, Win8 standard (uptodate), Centrino n 6235.
Firstly I've noted, like others, if I roll back to the MS drivers with Win8 then it's fine.
I was using a Netgear DG834 AP and all the drivers updates I've tried this year, up to 15.6.1 would experience the same slow down and, several minutes later, disconnect, requiring a reboot. However it should be noted that the laptop never disconnected from my Office WiFi (no idea what APs they're using).
So I switched my AP for a Netgear WN802T v2 and ran the 15.6.1 drivers again - this time it's fine unless I run a really long download e.g. 200Mb+, then it will drop the connection (always). Otherwise, occasionally it will still slow down as I can see from input lag in telnet sessions and slow browsing (which will be fine on other PCs in the same subnet) but it won't otherwise stop.
At my brother's house however, it manifests all the old behaviour that it did on my DG834. Connection dropped roughly every 20-40min requiring one or more reboots to re-establish. No idea what Sky router he's using though, will need to check.
Turning off all of the Intel services 'appears' to increase the interval between connection slowdowns but that's a subjective opinion.