Wirelessly posted (iPhone: Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_0 like Mac OS X; en-us) AppleWebKit/532.9 (KHTML, like Gecko) Version/4.0.5 Mobile/8A293 Safari/6531.22.7)
You may as well have asked if 4.0.1 helped your mortgage interest rate. Seeing as how apple hasn't even officially acknowledged the prox sensor issue, and made no mention of it in the 4.0.1 release notes, my guess is that anyone who thinks 4.0.1 fixed it is merely enjoying the effects of a reboot.