So far, I opened the Citi Exec, primarily for the 100k bonus. I have the Amex $500 credit waiting ($700 total since I haven't used the normal $200 yet either). I can't decide whether I'll keep both, or if I'll use the $500 Amex credit to buy a club membership and close the Citi once the bonus posts. I may push the decision until next year - keep the Citi for lounges this year and buy $700 in GCs with the Amex.
I'm keeping the Platinum though. Amex has tremendous customer service compared to Citi and Chase and I still get a ton of value out of FHR alone. Plus, starting this year I'm flying AS more (status match), and the PP Select is nice for their lounges.
I'm curious to see what Amex does next year. This year they threw $500 at me to buy a membership. If I use it for that purpose, I wonder if they'll keep it going. It's a lot of money, but if you only do it for the cardholders actually using it to purchase the lounge membership, I bet it's worth Amex's while - at least on those of us that use the card for everyday spend as well.