It depends what you're after.

It only makes sense for airlines which are 1:1 out of IDC (eg Singapore, Finnair) or who are not in the UK scheme (Qatar, Malaysia, Jumeirah Hotels).

There isn't any sort of sign up bonus on the cards at present.

Even for Singapore, the card fee even with a Green would outweigh the extra miles unless you are moving 100k Amex points.

I should say that Amex UK to Amex IDC to Jumeirah is outstanding. I have just booked another 10 days in Dubai for half term and got over 3p per UK Amex point, albeit I did my last transfer at $1.59. Our last two Dubai holidays were also fully paid this way.

This thread may well be the most valuable tip I have ever got from FT!