It's funny to me how many businesses I go to accept Apple Pay and don't actually realize it. I've seen people at the register at multiple grocery stores and even a restaurant outright surprised to see me use it, although one place actually advertises it on the display now (and their chip readers don't even work).
Personally, it's funny to me how it seems like the smaller places have much better support than the larger ones. Looking at the list of places I shop relatively regularly, we've got:
Accepts ApplePay:
Local single-location grocery store
Local two-location natural foods co-op
Local single-location pharmacy
Local lumber yard
Grocery Outlet (discount groceries)
Doesn't accept ApplePay:
Safeway
CVS
Costco
Ace hardware store
Local hardware store
Basically, all but one of the local places I shop do, and all but one of the big chains don't. I tend to shop local anyway, but it's actively encouraged me to avoid the other places, and I'd pick Walgreens over CVS just based on that if the nearest Walgreens wasn't 15 miles away instead of walking distance.
I do probably 90% of my shopping at the places that do accept it, so to me it's way more often than not.
I got the opportunity to try ApplePay on the web yesterday when my wife bought some shoes online and holy crap is that convenient. Click a button on my Mac, touch the fingerprint sensor on my phone, and boom, all my info is there and the order is complete! My wife couldn't believe it was that easy.