I'd like to weigh in here. Have had issues with the Intel Wireless-N 7260 since I got my computer. Tried every single driver and every single setting, like many others. My answers to the above questions:
1. 2.4 GHz
2. Windows 8.1 (x64)
3. Every network I've connected to thus far.
4. A fair amount, 6-8.
5. As previously stated before, it's very noticeable while gaming. But even browsing I'll have a random delayed response, and doing a speed-test gives extremely varied results when run consecutively.
6. Not sure. Disabling certain things, changing settings etc yields mixed results, but the connectivity issue still remains. So I guess, no.
7. Lenovo IdeaPad Y510P
8. Intel Wireless-N 7260 (yes it was installed by Lenovo)
I've tried a variety of PROSet drivers, all to no avail. Hopefully this issue can be plugged soon enough.
EDIT: I've just installed the 17.0.5.8, previously this driver was even worse than any 16, but disabled the U-APSD support seems to have significant change. I'll do some tests and update soon.
EDIT 2: The problem is definitely a whole lot better, but I don't believe it is fully fixed. The connectivity spikes are less frequent and less drastic, but are still visible. I'll keep trying some things and let you know.
EDIT 3: Disabling WMM also seems to yield a better result, but still varied. Problem still seems unfixed.