I had a great 4 year run with my F and over a decade with Lexus but it was time to try something different. I've had my 2015 GT-R Premium for over a week now and its performance so far lives up to the hype. The thing is incredibly fast! As others have mentioned you need to track it to really feel its full potential. You also give up some luxury that comes with Lexus that I have taken for granted (what no memory seat buttons??). They are in different leagues and given the choice I would have kept both. I hope to jump back into a Lexus at some point. My F was reliable, fast and luxurious rolled into one. The sound of the V8 cannot be compared even to the GT-R. Here are some pictures of the new beast. I'll still be around CL like some of the other former IS-F owners.
Thats a nice upgrade for sure ...i was contemplating on trading in the F for a GTR also, but having a family and all now, the F suits things much better with 4 doors.
Congrats on your new GTR! I almost upgraded to a 2009 GTR when i sold my is350. The only thing that held me back was that it was a 2 door. I needed a 4 door so i upgraded to the ISF. Enjoy and let us know how it goes.