I see they are now accepting suite night awards for the executive suite. I've been upgraded to that room once or twice and it is very nice. I like it better than the suites at the W and the Westin, but you're stuck with lounge breakfast (which was fine, but very overcrowded in my experience) instead of the nice restaurant platinum breakfast offered at the W and Westin.
There aren't many executive suites, so i'm sure this will still be a tough upgrade to get, but it's great to have the chance to confirm it in advance now.