Just logged into my account. It was 3000pts for a redemption at Quagalinos for a 3 course meal for one person. Looking at Quag's current set menu offering, this was worth around £25. (Of course add a side dish and compulsory tip and you're looking at £33 before booze)
3000 points now gives you £20 voucher/cheque to be used up within 180 days (and allow up to 6 weeks for them to post the cheque to you) so you could say this devaluation is £5 at least at this range.
But if I've read the T&Cs right, the points only expire now if you have no activitiy in 12 months, whereas before they would expire after 12 months after when you earnt them, so at least you have a chance to accumulate more if you only go out once a month or if you want to keep accumalating them. However I've also noticed you only earn 100pts per visit now.

Maybe we'll be making lots of bookings for 1 instead now and "bumping into friends" when we get there!!
We'll need the Amextoptreats points just to earn what we were before! Unless that's changed now too......