Most people don't go to family memorial service so I don't think it's a big deal at all
In the Royal Family they do - as demonstrated by the fact that almost everyone was present.
I agree with Bertie that whether the Queen gave her consent or not is irrelevant, it should never have even entered William's head to ask for it. I don't think it suggests he hates his father but I do think it was disrespectful towards the Queen Mother and Princess Margaret. To me it is just compounded by the fact the absence was caused by a holiday.
I do think William was probably spoiled by both parents as a consequence of the nasty divorce. As a result of Diana's early death I think he and Harry were probably indulged (I have no proof of either by the way, it's just an opinion).
I also think it's another example of the double standards of the British press. Had either York girl not been there because they chose to go skiing instead (and I'm not particularly a fan of the York family), there would have been plenty of criticism aimed at them.