Once - amazing experience but not sure I would do it again (especially if I was paying?). It was a totally different experience to other planes and not really appropriate to compare with First Class on a 747 etc as designed for completely different purposes.
My memories - concorde lounge in those days was amazing (!!), then how narrow and cosy the plane was, the bucket-style seats, brilliant service, the curvature of the earth, the darkness of the sky, the heat against the windows and the thrill of mach 1 and then 2. I was like a little kid and saddened by all the "regulars" around me who were totally non-plussed by the whole thing.
Best thing was senior colleague who I didn't get on with had caught the 747 earlier and I missed it (the last one) due to traffic to H'row and was put on Concorde and arrived before him!! He was really pissed off as he had never been on C'corde!
I really miss seeing Concorde. It flew over the golf course where I use to play at 10:30 every Saturday morning and we never tired of watching it. A thing of rare beauty. Sad that it was a commercial disaster.