5Mpixel != 5Mpixel != 5Mpixel
Megapixels are meaningless, it's the size of the image sensor compared to those megapixels that matter. I haven't seen the size of sensor the IPhone uses, if it even has a dedicated sensor but I image it's smaller than those of todays digital point and shoots let alone those of SLR's. If people want their Iphones to be capable of allowing users to take pictures like those of P&S's, they need to ask Apple to put a larger sensor and better optics on it.
I don't see that happening anytime soon, so a 5MP camera will be a waste of memory.
You beat me to it.. I about puked when I saw the "megapixel myth" rearing it's ugly head. What people need to know, as you said, is that the amount of pixels is almost meaningless as a reference for picture quality in modern cameras.
Unfortunately, the primary components/specifications that do affect the picture quality, such as the CCD/CMOS sensor size, sensor quality/architecture, imaging processing circuitry, and firmware are not usually advertised on the box, but they can be found for a certain camera model if you google.
Case in point: an 8-megapixel point-and-shoot camera would be lucky to have a sensor with an area
1/10 of an 8-megapixel Digital SLR. Similarly, an 8-megapixel cellphone's sensor would probably be 1/4th or 1/8th the size of the point-and-shoot.
(side note: If you want to see a great article about this, see
http://www.dpreview.com/learn/?/key=sensor+sizes )
The tiny sensor sizes in these cellphones
are adequate (for some people) for quick snapshots in bright daylight, but they all but fall apart in anything but perfect light because their light capture surface area is so small they can't capture sufficient light. This results in major NOISE, poor color reproduction, and many a blurry photo because the sensor has to increase the exposure time to get enough light. Now of course, in addition to this, the image processing chip and firmware in a phone camera is much less robust.
So how are you supposed to know how any camera will perform? Most important thing is to read the reviews and not listen to all the marketing-speak.