There is virtually no unique technology in Apple products, so the "high R&D spend" story is nonsense. I've been in electronics since the 1970s...
They are good at producing stylish stuff, at a level of build quality which is up with the best in consumer IT gear (though IME definitely not up to the level of say Lenovo), and they market it very cleverly to make the items very desirable.
Fashion breeds fashion and once the bandwagon got rolling they kept it rolling. But it could come to a halt... look at where Myspace is now, for example. Fashion icons come and go. Apple is like Facebook.
Apple products are nothing that any technologically capable company cannot make. For example the Samsung 10" Galaxy tablet is virtually the same as the Ipad, with the apparent differences being just the O/S, and IOS implements the finger gestures better.
And the Iphone is actually a pretty crap phone. Even a £10 phone from Asda is a better phone. At home we have an Iphone4 (which frequently fails to work for inexplicable reasons, and has already been replaced once under warranty) and an Ipad2 (which is mostly OK but has weird wifi issues, along with seemingly many others, and Apple have also replaced that under warranty when its HDMI output was found to be dead). That's a 100% failure rate in our household, reducing to 66% if I count the Imac I bought for my son who lives away.
Steve Jobs was by all accounts a thoroughly nasty character whose nastiness no doubt contributed to the polarisation of views on the company.
Apple use their massive power to shaft Chinese subcontractors into making the stuff for tuppence while they make a few hundred $ gross profit on every one. Of course, nobody is now going to bomb the price so all the other smartphone makers are now playing the same game and milking the market for all it will pay (currently).
Their appstore is full of banal crap. About 99% of the 200,000 or so apps perform no useful function. This becomes obvious when you start looking for something... and the stupid partitioning of apps and their private data means one has to buy multiple similar apps just to do one job.
I would not buy Apple shares because I cannot see the upside. They have no unique technology. They have a slick O/S but that is "just software". They are selling because they are fashionable, not because they are somehow excellent compared to anybody else.