If I may add something:
ipad2,1 or ipad2,4 are not HW Revisions, they are model identifiers.
Apple is famous for its secrecy, it helps build the magical hype that surrounds its products, so they're very good at not disclosing information such as different HW revisions. But if you disassemble a couple of ipad2,1 you'll mostly find different PCBs and/or different chips on them (even the LCD panel manufacturer varies).
With the iPad 2 Apple went even further and at some point in time it introduced a totally different model (with a new model identifier: iPad2,4) and marketed it under the same iPad2 name.
I think the rationale behind this is: If you advertise your product by its features (i.e. not by the chips you put inside it), you may sell two units which are identical on the outside but different inside and it's perfectly fine as long as they offer the user the same advertised features.
You'll probably never see a regular device or smartphone displaying its HW Rev anywhere.
Nexus devices are developer oriented, so they have a special bootloader that displays the HW rev.
Moreover, it's not always true that HW Rev 2 is always Better than HW Rev 1.
A hardware revision bump could be just to accommodate changes related to some part's supply constraints. It doesn't necessarily imply that some bug has been fixed (yeah of course, in the case of the nexus4 this happened and we even have documented evidence about).
In fact I suspect that if you are having troubles with wireless charging a rev10 Nexus4, then Google will accept an RMA.
IMHO very few people uses wireless chargers (yet) so rev10 phones will be fine for most of the users.
Originally Posted by draugaz
Or there is another even more glaring example: ipad2 was converted from ipad2,1 45nm SoC to ipad 2,4 32nm SoC bringing like 20-30% better battery life which is pretty significant. For some time you could buy any of them, it was just a pure question of luck. There was no way to tell which one is which without opening the box and installing some software.
No one got their ipads replaced because of this, even if they bought it after rev 2,4 was already available and they paid the same money.