I totally agree. I've had the 400i's and the Alpha Primes as complementary headphones for a couple years now. I always felt they were a fantastic pairing, that left little room for anything else to be desired. Until I bought the Sennheiser HD 800S's, that is. I freely admit I've been using the Sennheiser's more often than all my other headphones combined, but at that price I'd better be listening to them, LOL.
I did take some time this past weekend to listen exclusively to the 400i's, and I have to say I'm as impressed today as I was when I wrote my effusive review after I first got them.
As far as this ridiculous claim about "graininess" is concerned, there's nothing I enjoy more than reading a relative newbie lecture me and my friends about how "we don't know how to listen to music yet", and the proof being that we don't agree with the opinion. I have yet to hear so much as hint of graininess, and that's with some fairly decent gear, thank you very much. What I do hear, especially after paying attention to the HD 800S's for so long, is a loss of detail in complex musical passages. Dream Theater is a good example of this, as when the band shifts into fifth gear the 400i's lose a decent amount of detail and definition.
Other than that, these are simply ridiculously fun headphones to listen to, especially considering the price. Still one of the best bargains in audio, IMHO.
YMMV and all that…