I know this is an old thread recently revived, but I'll reply for the sake of those who are discovering it for the first time.
I have the track pack with carbon buckets, and will not buy another McLaren without them. They change the experience from a sleek road car to that of a snug race car. So if that's the experience you want, don't settle for less. Actually, I don't think I'll ever buy another performance car in general without bucket seats like this.