As I have access to multiple PS3s and screens and copies of GT5 I decided to give this a go so am now going to post impressions.
Also as these are my friends screens so they don't all match, I imagine a version using identical screens with smaller bezels would be very impressive.
First, wow, the sense of speed is so much better, when you see the side of the road whizzing past it is quite impressive!
It was quite simple to set up, I was concerned it was going to take some time and would need ethernet cables but it works fine using the wireless connectivity.
The game ony uses multiscreen when racing or in the race menu, at all other times only the main screen shows menus with the side screens showing the GT symbol as per loading screens.
The multiscreen works for both racing and replays, in race you can still look left and right giving you a very, very wide range of view.
Looking right
And left
And behind!
The multiscreen works online also, very useful for checking positions of opponents cars.
Obviously with standard cars there is no cockpit but the bumper/1st person view works well.
looking right
and left
And in 3rd person view
And finally in replays, of which I struggled to get a good picture!
If you are rich enough go for it, it works very well! I am lucky enough to try it for free.
Am still to check about using the adjustable fov in single screen mode.