Your second question. Quite a lot of trip reports to give you an idea of the F experience. Benefits include the F lounge in DXB (which I feel is a definite improvement on the J lounges), more personal space, better wine and better presentation of a wider range of food. If the above appeal I would go for it on a day flight (but I view miles as a transient benefit that the airline may devalue at any point so I prefer to spend them).