My experience with Explorer:
Signed up online and account automatically linked to my existing Accent (as expected). Called and asked to separate the accounts. They were indeed separated immediately but was told it takes up to 5 working days to create Gateway. Meanwhile I can spend on the card and points will be backtracked to the new programme. Spent > $1500 and points indeed showed up on Gateway but no bonus. Later spent again > $1500 and the 100K finally showed up.
Now my dilemma is what to do next:
1. Keep the points in the account and ask to merge back with Accent, hoping the points will have greater value but also risking loosing them altogether.
2. Transfer the points to KF and then ask to merge.
3. Keep Gateway, earn less miles but enjoy the promos
Congrats on getting the bonus points. Personally, I wouldn't get too greedy... asking to unlink Ascent, taking delivery of the bonus points under Gateway, and then asking AMEX to re-link back to Ascent (with or without the bonus points in your account) could risk setting off warning flags.