Apple rushed the iPhone 4 to market with insufficient testing. It simply is not ready for prime time.
Apple was worried about the Samsung assault with their very successful Android Galaxy S model on each of the Big 4 carries in the USA. This is the first time that any major manufacturer has released their top of the line smartphone on AT&T, T-Mobile, Verizon, and Sprint all in a matter of the same 90 day period. This phone has been very successful outside of the US, and now we are getting it here.
In addition, you have the new Motorola DROID X, and many other Android phones coming into the US between now and the end of the year. They are all eager to grab market share.
Android has been identified as Apple's biggest threat.
Thats why so many fanboys are badmouthing it on this forum.