It worked alright for me most of the time but there has been an issue where if there was no internet connectivity when I open the app
(because I use T-Mobile and they suck in Austin... well not just Austin but that's another topic)
It completely fails to pop up the dialog to show my room number and let me open the door.
They have just (last week) updated the SPG App for iOS and the changelog talks of improvements and bug fixes to keyless.
FWIW I didn't get an e-mail offering bonus points for Keyless. Maybe because I already used Keyless half a dozen times or my address is in HK.. it may be targeted after all....?