Beware, because Delta has horrible redempetion rates. For ex, they may give you a 20% bonus, but inflate the award rate 50% from what they advertise. Not a good deal IMO. However, Delta is good for partner redemption, which are all at the "low" advertised level.

Continental hasn't run a transfer promo in a long time and its speculated they may leave Amex MR once the merger with United goes through.