The issue seems to be a significant drop in range now available to the One X. All other wireless devices in our house have no issues with full coverage throughout the house (and this was the case with the One X prior to upgrade), but the One X has abysmal range. When in the lounge (which is where I use it most), connectivity is either non existant or very weak. The lounge is on the level below, and one room over (approximately 10-15 metres) from where our router (Apple Extreme) is situated.
Because I only started suffering these issues after the upgrade, and because all other devices seem to be OK, I'm hesitant to blame the wifi network itself. I'm also hoping its not a hardware limitation of the One X, as performance was fine until the OS upgrade.
Version information is as follows:-
Android version: 4.1.4
HTC Sense version: 4+
Software number: 3.17.781.2
HTC SDK API level: 4.63
Kernel version: 3.1.10-ga3fa789
Baseband version: 5.1204.163W.30
Build number 3.17.781.2 CL140020 release-keys