They're useful. Texts/Instagram real time GPS etc.. all show up, you can read & clear notifications, it's a great convenience to not have to take the phone out to clear/check something.
some app support, like shazam, useful.
one the biggest benefits - if I'm driving and get a text I can read it off the watch from 2 feet away, text can also be replied to via the watch. plus u can scroll the entire text convo.. very clutch for when I'm using my phone for GPS and don't want to unmount/mount
it's not a game changer, but for $150, it's worth it.