(Update July 16: Nope. Better, but still messed up. See update below)
So I just patched my iphone 4 with ios 4.0.1. While consumers, and specifically tech sites were going nuts about the reception, I just installed the bumper and it fixed the problem for me. That was pretty much a non issue with me post the bumper.
The one issue that really bugged me was the buggy proximity sensor. Every time I put the phone to my ear, with a bit of movement, I would either mute the call or add another line. Most irritating. My initial tests seem to indicate that ios 4.0.1 fixes this nuisance. I certainly hope that is true as I continue to use it. I’ve been reading others say it does not fix it, but I tried 3-4 calls now and I did not experience that issue. But time will tell.
I don’t really care if they increased the bar size, decreased the bar count and what not.
What do you feel? Did 4.0.1 fix the proximity sensor bug?
Update: July 16:
No, 4.0.1 does not completely fix this. It seems to certainly be better, but I can’t say its completely fixed. I’ve made several calls now and I’ve managed to:
a) Start Facetime by mistake
b) Put a call on mute
without my doing anything out of the normal (sitting on my chair, talking to a colleague over the phone)
Fortunately, Jobs publicly announced the proximity sensor fix in the next release. I look forward to it, and a refund on my bumper.
And the apple antenna page is cool too.
on 
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I too had the proximity sensor problem, most annoying thing ever. But since ive installed 4.0.1 it doesnt seem like I have it anymore, I sure hope it stays this way..
[...] (Figured out a week after I bought the phone – after I realized I can’t be making the same mistake over and over again) – the damn proximity sensor. If I hold it to my ear, and wiggle it a wee bit, the screen comes alive and my ear presses either the mute, the hold, or add call button. Supreme nuisance. (Update: Does ios4.0.1 fix this?) [...]
Seemed to fix it for me. Using my finger, the screen now turns off at about 1″ away. Pre-update was 1/4″. This was just a single phone call – so we’ll see how it goes long term.
@all, looks like the honeymoon fix got a reality check for me :-) Inadvertent FaceTime and Muting while in a call.
The clear suspect in this bizarre behavior appears to be the iPhone 4's proximity sensor, mouthful of a term that describes the sensor that detects your face's location relative to the screen, and enables or disables the display accordingly. On the iPhone 3GS, the proximity sensor was located to the left of the earpiece speaker. But that space on iPhone 4 is now occupied by the front-facing camera, and the proximity sensor is above the earpiece.