They felt great, but I will caveat that by saying I am a beginner. I have only autocrossed Miatas and MR2s on Victoracers and V710s and I have only had my GT-R for a few months so this is my first time trying a setup other than the RE070Rs on the stock wheels.
The diameter difference is about 5% smaller and I felt like there was a difference in acceleration because of this. However this setup is too low for me to feel comfortable driving around on the street. I scraped my front and rear diffuser a few times. You cannot tell from the picture, but I think the 295s in front stick out a bit past the fender. I am guessing on this, but because there is a lot of gap there may not be enough suspension travel for the tire to hit the fender. On a taller tire that is 295 or wider you might have issues.
Someone else I know is planning to go to a 19" wheel to get better brake cooling, I am not sure how much truth there is to that. For a track setup 18" are cheaper, lighter, smaller diameter for more acceleration, and there are more tire options for the Toyo R888 and probably other tires as well so that is why I went with 18". For a street setup, you will want a bigger wheel. This wheel also comes in 19x10.5 and 20x10.5 for an inexpensive nice looking wheel.
Also for a square setup, this is a great wheel because 10.5 is probably the widest you want in front. For a staggered setup if you want to run 305 or wider on the rear you will want a wider wheel and this wheel only goes up to 10.5.