Interestingly, Joe also didn't take exception to the original questionner referring to the Wi-fi issue as a 'bug' (as opposed to a 'feature'). Here's Joe's tweet:
@ssimpson205 Someone is gonna yell at me for saying this, but...fix is coming. :)Sshh.Just promise me a little patience though.
— joebelfiore (@joebelfiore) November 10, 2012
The Wi-fi issue didn't just annoy me (the delay was often up to eight seconds under Windows Phone 7.5, though seems to be much reduced for Windows Phone 8), it sparked a mini cottage industry in apps which did everything they could do keep wi-fi going even with the screen off. Perhaps the cleverest was Active Wifi, which spoofed a paused music track playback, and which I reviewed here but have since stopped using because it had too great an impact on battery life.
It's not clear from Joe's tweet whether the 'fix' will apply to just Windows Phone 8 or to Windows Phone 7.5/7.8 too. I suspect the former, but am prepared to be pleasantly surprised!