Only nismos I have heared of "failing" are those which run aftermarket cats.
You will also hear about more Nismo failings because there are a lot more of them about that the scorpion
(I'm not saying the scorpion is crap, but I'd like to see how it looks after a few winters)
A decent titanium exhuast is gonna set you back a minimum of £2k & even then it wont include a y-pipe (Price up an Amuse y-pipe if you fancy a laugh ), the one I'm looking at is around the price of a Nismo & thats just a Y-pipe back single exit.
The Nismo is a lot of money, but its also one of very few that actually come with a y-pipe
**Completley impartial view, I only buy Nismo stuff if I absolutley have to **