Nokia, RIM and Htc just gave us PR's bs.
Not a single demonstration of their phones to be "death grip free".
Nokia and RIM, in particular, responded with a single statement each (no on-going smear campaign as Apple is currently doing) of essentially "This is your own self-made problem, leave us out of it.". This is not Apple defending themselves against the horrors of other manufacturers attacking them -- not a single manufacturer was commenting on or using Apple's antenna problem to make themselves look superior. This is solely Apple lashing out against anyone near them in an extremely immature, egotistical (hi sjobs) attempt to make themselves look better.
All these companies need to do, in my mind, was to issues their single response each -- "Leave us out of your problems, Apple." They don't have anything to prove, they probably don't even have to do anything to 'fix' their reputations except let Apple throw this little tantrum, making Apple look like a toddler who didn't get ice cream.
As far as the comparisons between phones and holding them, yes, phones will change signal strengths based on what is obscuring the antenna. The best signal will come with a fully unobstructed line-of-sight to the cell tower. The amount (and how difficult it is to cause) is what varies significantly.
The iPhone 4 is reported to be
extremely easy to cause in any location with a weaker (even though it may still be 5-bars) signal, with as little as a single finger in the right place.
This drop will not be visible for everyone since you cannot read the actual dBm level on a non-jailbroken phone, and the drop in signal is not large enough to drop from completely 'full' 5-bars to less than 5-bars. Yes, the word "visible" does imply that it should occur (visible or not) on every iPhone 4, since it's a design flaw, not a manufacturing flaw.
Similarly, for other manufacturers, it depends on how strong the signal is, how the signal is mapped into bars, and how sensitive the antennas are to being blocked. However, all the discussions I've seen point towards the problem occurring in mostly absurd manners (such as near-crushing the phone, covering the entire phone with two hands, etc.), and only in very specific signal conditions (similar to the conditions that cause the drop in iPhone 4 signal display -- being at the lower-end of a bar range).
The problem is not that phone antennas are perfect, or that the iPhone 4's signal drops when
zomg no other phone does. The problem is how easy it is to cause (as little as one finger in the right place), the cause of the problem ('bridging' the antenna, which entirely changes the properties of it -- this is most comparable to taking your other smartphone apart and manually grasping the bare antenna), the severity of the problem (larger raw signal drop than other phones -- ~25 dBm -- as well as significant dropped calls/data connections), and Apple's reaction (TEMPER TANTRUM).
Unfortunately, this little temper tantrum may also be caused by a different problem with the world -- profits and lawsuits. If they manned up and said "yes, we screwed up" they'd be opening themselves up to massive class-action lawsuits and serious drops in stocks. Which could get them sued (again!) by shareholders for not maximising profits. So they instead have to be as noisy, obnoxious, and vocal as they can about how their phone is perfect (at least compared to other phones), no matter if they
know there's a major design flaw or not.
Perhaps the most telling result will be the design of the iPhone 5. If they keep the external, uninsulated antennas, then they
actually believe their design isn't a problem. If they don't keep them, then they
know the design was a failure.