So today the iPhone 4 I have had since Tuesday developed the "proximity issue" - after my call was ended it was hard to snap it out of the talking-with-it-by-my-face mode to hang up.

However it was easily fixed. I read the article on Macworld and did a Reset>Reset Network Settings, and now it is working fine, tested it and even got to take a real call with no issue. And the only fallout from the reset seems to have been that I had to reconnect to my home wifi network.

So if it happens to you, try Reset>Reset Network Settings before doing anything more drastic!