It has worked for me sporadically. I didn’t even know it was a feature of the watchOS update until it “spoke” to me. I hate that it doesn’t reliably work though because I do actually find it very motivating. The second time it worked, I ran 6 miles and it motivated me to run faster each mile, cutting off almost 90 seconds from mile 1 to mile 6. Now I haven’t gotten notifications in around a week.