It doesn't bother me really, after all everyone seems to have one. 1/4 of the people who read these books most likely read it on one. It is a whole lot easier to write iPad than tablet PC over and over and over again. Besides, in the first book he gives her a Mac computer. Those who are Mac fans always want to make sure the whole world knows they are and why. Yes, I am making generalizations and there are always exceptions to the Mac braggers.
I don't think it was product placement as much as it was just wish fulfillment and James trying to fit things in that she assumes people use constantly. The Fifty Shades trilogy is pretty obviously fantasywank, so throwing in items that you want to match the sex you wish you could have IRL (even though you know it doesn't work that way) is pretty standard.
Well the Audi references can very well be left over from when "Christian" was "Edward," as "Twilight"s sparkly male lead has a strong affinity for the brand. As far as the constant Apple product references, I'd have to chock it up to E.L. James' interpretation of the toys that rich people have. Apple is more of a luxury brand when it comes to electronics than say...Dell.
I did note a lot of product placement. Audi, with the statement that they do make the safest in their class, and she wore Louboutins, she mentioned that. It did annoy me a bit, but I guess she thought it added to the fantasy element--buy my love with a Saab, an Ipad, a Blackberry and some Louboutin stilettos.