Just spent almost 2 weeks in the US, mostly in Marriott properties. Here's the tally of success:

Residence Inn Marina Del Rey - SNA declined, upgraded to a partial seaview
Courtyard Palm Springs - SNA accepted! Upgraded to a 1 bed suite
The EngLish Hotel Las Vegas - SNA declined, no upgrade
JW Marriott Resort Las Vegas - SNA declined, don't think we were upgraded, however one weird thing happened. We took points instead of breakfast as we had a 241 for the buffet. Had the buffet and charged it to the room. At checkout she asked if we had breakfast, we said yes, and she said "I'll take care of that" and took it off the bill!
Springhill Suites Springdale (Zion) - didn't bother with the SNA, no upgrade.
The Avalon Beverly Hills - don't think they accepted SNAs and no upgrade or breakfast offered.