Yeah, Blizzard has the metrics. If people even mildly disliked the new flying, Blizzard would have ditched it, not added it to the main game and then to the next expansion.
Blizzard have a very clear goal at this time to grow the playerbase and make people happy and keep them happy - something that hasn't always been true in WoW. Blizzard pretty rapidly went from being shocked at how many people liked WoW when they released it (Rob Pardo himself said they expected to sell through WoW's stock in 12 months, not before the first month was up), to by the time TBC came out, completely and totally taking the playerbase and its continued expansion absolutely for granted, even though it actually only lasted about three-four years after TBC. They started doing stuff they knew perfectly well mostly players had little interest in or actively didn't want (no-one asked for RealID, for example, and huge swathes of people opposed it, and Blizzard themselves acknowledged less than 0.5% of players ever took down even one boss in the Sunwell whilst it was still relevant content - as compared to 40% with Molten Core), stuff that was essentially "for themselves". Only when Cata being so obnoxious that it finally got people quitting in droves did they realize they might have fucked up.
Anyway, point is, Blizzard aren't going to pursue anything that people definitely don't like, because it won't achieve their goals. So anyone who thinks the new flying isn't broadly popular is out of their mind. I have friend who has just started DF and whilst she's still pretty wobbly with the flying and has complained about it, she's already excitedly collecting glyphs and was saying she could tell that if she could get to 5-6 bubbles this would actually be an awesome way to get around (this before she even knew that was the max).