I sold my ISF in July, very reluctantly and now have a GS450h F Sport which I love.
I miss the raw power of the ISF and the rarity value, but having said that the 0-60 of F Sport is only just over a second slower than the ISF, not bad for a very heavy car.
When it is in Sport + mode, the rear wheels turn slightly to aid cornering and the handling is good.
The technology of the GS is amazing with its 12.3 inch screen and many other extras.
Don't get me wrong, I do miss my ISF but in all honesty, I wouldn't change back.
Just had a black carbon fibre roof added together with with mirrors, looks the business.