As I mentioned before, I couldn't sit in the rearseats and be driven around. However I did sit in the stationary showroom cars with the rear seats reclined and then moved back into their normal position. I found them comfortable and similar to the Civic - a long trip in the grande will confirm this - it could be a few cms more than the Civic but for what I could tell, it was more or less the same. What worries me is that the grande comes with leather/leatherite seats only - and leather seats in a car parked in the June heat for a few hours won't be very comfortable.
Based on the fact that the grande has reclining Seats, and the 'famous cushion' suspension that we all know the Corolla has, I'm sure it will be more comfortable on long trips - but to be very honest, I don't feel tired in the civic either. But the grandes reclining Seats will give an edge as far as back seat comfort is concerned.
The cabin noise is more or less the same as the Civic - but it's better than the previous generation of the Corolla, maybe because this could have padded doors (need confirmation about this though).
If you're planning on buying the basic version,you won't be getting rear Reclining Seats and will miss out on a few other goodies. You could have a look at the specs sheet I've added somewhere in this thread.
PS: yes that's one of the sales staff taking a nice break. Poor sales guys/women were extremely busy taking calls and showing the grande to everyone - they were extremely courteous and well mannered. So he deserves this short break