Yes the R35 is a big step up from the old GTR's. Highly modified GTR's (costing about the same as an R35 in total) wouldn't be far behind re performance, but tech-wise the R35 blasts away.
A big difference i find is the old GTR's are like a platform upon which boundless kW can be extracted. That makes it really exciting, like opening up a massive easter egg with little wastegates rattling inside.
The R35, from the reports, appears to be an awesome purpose built sports car but without the strength to be pushed 50-60% harder (like 32/3/4's).
So in that sense it's becoming an 'owners' car, if you will, rather than a modifier's car. It's so great (and pushed closer to it's mechanical limits) compared to yester-gears GTR's that it can't really have too much modifying done (without re-engineering the manifolds/head/block/rotating assembly/tranny etc.).
It's already so well honed and balanced it bores me.