You may have been reading about the antenna reception problems that have been reported in the media lately. One ZDNet reporter even called his iPhone a lemon due to these and other problems.
I have to admit that as much as I love my iPhone 4, I am experiencing intermittent and weird problems related to the reception and proximity sensors. I followed Apple's recommendation by using a case to avoid touching the antenna part of iPhone, but that cause other problems. The case I purchased somehow cause other problems related to the light sensors. When the case is on the phone and I turn it on, the iPhone appears to think that the room is darker than it actually is and keeps the backlight very dim, making it difficult to read in a bright room. There's a workaround for this, which is to turn off the light sensors, but I prefer not to use that. I'm going back to using my iPhone without a case for now.
Unfortunately, Apple's explanation for the reception problem doesn't make a lot of sense. The planned fix only addresses a problem with the way the reception bars are displayed, not the actual antenna problem. Also, there's no word yet on whether the proximity sensor problem is hardware or software related. Obviously, a software issue can be addressed with a patch, but a hardware issue requires a recall, which Apple is unlikely to do.
In the meantime, it's still difficult to get an iPhone 4 today. People are buying them like crazy. It's doubtful that these issues will have a long term impact on sales of the iPhone 4, but I wish they can be resolved.