Having sold both iPhones and Android phones for almost a year now, I think I'm in a place where I can make a well informed comment about the buying habits of people who buy these phones:
iPhone buyers:
Generally, most people come into the shop and ask what the prices on an iPhone are even if they're looking for something completely different, almost in the hope that our prices will be different (/cheaper) than anywhere else (which of course, they're not [apart from 3 who seem to be using witchcraft to sustain their pricing strategy

]).
Most people want an iPhone because (as has been said many times in this thread) it's shiny, trendy, expensive and all their friends have one so they must also get one. These people know nothing about ROMs, apps, different OS's and most didn't even know that they COULD copy and paste on a phone for years before apple made a big thing about it.
However, they also are a bit more open minded to other options when it comes to alternatives like android (mainly after being told the price for an iphone), but I'll explain more about that when I go into android buyers.
You also get a few people who want an iphone and will get an iphone no matter the cost, the alternatives available or even if it means they have to give up the use of their left leg. These people tend to be more techy and well informed but some are just trendy and NEED the latest gadget in their lives.
This mentality is very similar to the "teenage girl wants a blackberry" mentality.
As I work in a phone shop in Bath, we get quite a lot of wealthy customers come in. I recently had one gentlemen who bough two iphone 4's for his two daughters (aged 12 and 14), both on the £45 24 month contract plus £29 for each phone upfront. Just because his daughters wanted them. They didn't know why they wanted them, but none the less they wouldn't consider anything else. You just think........ why?!
Android buyers:
A lot of people that buy android phones in our store, are people who originally came in looking to get an iphone. They want something with a touch screen and gadgety and cool but collapse when they see the price of an iphone and so want to get as close to one as possible without paying the price.
After us explaining to them that, actually, for what they want the phone to do, they could have a wildfire or defy for example which is half the price and does almost exactly the same thing, they come to their senses and go in the android direction.
There is however a small caveat to these sorts of buyers. No matter how much we explain how to use the phone, set up a google mail account and go and download apps, they will never, ever make any decent use of the phone and just use the basic features it came with.
This problem arises, a lot of the time, from these people being told by their techy friends to get the htc desire hd or samsung galaxy s because it's amazing and you can do lots with it, when in fact, a nokia c5 would suffice or at most, a wildfire.
We see so many people come in with android phones that have never had apps downloaded onto them and have never backed up their contacts. Either that, or they have created a googlemail account and downloaded apps, but, despite us warning them to remember the details, when the phone goes wrong and they come complaining to us about it, they suddenly forget them and we have to explain that their contacts will be lost as they're backed up to google and there's no way to get them back if they don't know their details.
I suppose non-techy people get a little bit confused with android as it takes a tiny bit of work to get the best out of it (i.e. set up a mail account and download the apps etc), where as with an iphone, there's no thinking involved at all as you're pretty much told what's best for you and you follow apples rules.
The best kind of people that come into my store are the well informed, relaxed techy types who have done their research and know exactly which phone they want, and 8/10 times they want an android phone such as a desire. They, will happily chat away with you for a while about different apps, the advantages and disadvantages of different handsets and their features and generally will be upgrading from an android phone such as a G1 or a hero anyway.
Conclusion
There are two sides to every story, and in my experience, I've sold more android phones to idiots than I have iPhones, but that's probably because they're cheaper and so they're available to a bigger market.
I myself use a jailbroken iphone 3GS 16gb and I've customised it to the hilt with various things so I guess I kinda get the best of both worlds.
I love android though, especially on the samsung galaxy s (touchwiz is fantastic as is swype, and yes I know you can get swype on other handsets) as it's so versatile and most of the apps are free.
I can pretty conclusively say that after showing people an android phone next to an iphone and explaining the price difference and the advantages/disadvantages, most people will end up going android. I just wish that more of them would put the effort in and get the best out of their phones.
Anyway these are just my observations, so you may disagree and have had different experiences with people yourself, but this is just what I've found.
Anywho,
MERRY CHRISTMAS!