I did as you did, counting only those explicitly stating that they have an iPhone 4 and noted all those who claimed they had reception issues vs those claiming they didn't. 16 iPhone 4 references in this thread in total.
The point remains that we're seeing an unusually high percentage of respondents with reception issues. Far higher than any previously reported problem with Apple kit that I'm aware of. I don't believe we can put this down to some kind of conspiracy to damage the iPhone 4's reputation.
Whether or not the issue is a serious one is up to the owner, but we're past the point where there's doubt that the issue is widespread. Even if 10% of the iPhones were affected, that would still be widespread in my estimation.
I wonder how many of the people who are pooh-poohing the problem would turn down a free replacement from Apple if it were offered.
Not many I'll wager.