More and more places are allowing it now that they had to get the fancy new chip terminals. I use it at my local grocery store, my local convenience stores, Subway, McDonalds (on the rare case I go), ToysRUs, Petco has it but I hardly ever go there. Panera was one of the first places to allow it. Walgreens is back to using it, they had stopped in hopes of getting Current C or whatever that was.
Each terminal is different and the clerks don't always know it works and are amazed when it does. If you see the little wifi looking thingy it should work, or if the display says 'tap' on it. My grocery store had no idea and when I tried it (it said 'tap' so I did) everyone just looked at me funny (I get that a lot anyway but this time it was for a reason). Pretty cool you got a notification though, I'd read that was coming but didn't know it was here.