I know the iPhone4 suffered from signal problems if held with a left hand, but I've just got an iPhone 4, and even if its sitting on a desk the signal (for any network) is a lot less than my Samsung phone.

For example with T-Mobile, the Samsung will show 4 or 5 bars (out of 5) yet the iPhone shows 1 or 2.

Same with Three or Vodafone. Is it the iPhone picking up a poor signal, or the other thinking its stronger than it really is?

Since there is no agreed definition of what the bars on a signal strength indicator mean there is no way to know.

The only way to be certain is if both phones indicate 5 bars for teh same amount of signal received. For the sake of explaining this. Let us say the Samsung indicates 5 for a signal of 5 volts and the iPhone 5 equals 10 volts (yes I know they are totally wrong units). If the signal is 4 volts then the Samsung will show 4 bars while the iPhone will show 2. but the signal is exactly the same.

So comparing signal strengths on two different makes of phone is not really going to tell you much. Even less so if they are different networks. There is nothing to say that two separate networks will have equal or anywhere near close signal strengths at any given location.

I have found iPhone 4 generally better than previous phones for signal quality.

Apple did a software update that changed the bars on the iPhone4 to give a more accurate indication of the signal being received.........

my phone shows 5 bananas, but your phone shows 2 potatoes.

the only comparison is the ability to make calls and send data.

i am quite often unable to make/receive calls on my iPhone or HTC Legend both are known to have issues in getting a signal. I have just got hold of the HTC Trophy 7 which always has a great signal at home and i am able to make/receive calls where ever i am in the house with out having to position the phone in a certain location to make it work!

Mobile networks have never wanted you to know signal problem areas and suchlike.
So the phone signal issue is no doubt a can of worms they avoid so as not to upset suppliers etc?

Apple changed their phones to have the high signal bars but have now reverted back to accurate signal bars. They also removed the more accurate digital signal readings from their phones.
The iPhone 4 might in fact be better or even on a par with that Trophy when held right.

Seem to me the above does it work/doesn't it work is the decent test.

Could be accurate or just more pessimistic.

In my experience the iPhone 4 gets a weaker signal than other phones when placed on a desk (and I'm using the reported signal strength in dBm rather than bars to reach this conclusion).

I can't find any information to suggest that the iPhone has particularly worse reception than any of its rivals, so I guess it's just a question of how each manufacturer decides to report signal strength. What I can say is, holding-it-wrongly aside, the iPhone 4 has markedly better reception than any iPhone before it.

However, that said, it is a known problem that iPhones drop calls, whereas there doesn't seem to be many (any?) reports of similar problems for other phones. So make of that what you will.