I have installed M3 control arms front and rear and rear subframe bushings and the B16 ERC suspension, I have the stock runflats still on so this should be a unique comparison as it excludes the tyres as a factor.
I have got the suspension set up as close to stock as possible which is 1cm lower than stock.
1stly, the rear bushings give a more connected feel to the rear tyres over bumps.
As for the suspension, the biggest difference is its a lot less harsh in both settings. In comfort setting it devours potholes where the stock suspension would make some passengers swear.
Over speed bumps there isnt too much difference between the 2 settings.
Over rough road surfaces the comfort mode seems a lot more comfortable than sport mode, big difference here and I feel this is the selling point.
One major downside is in comfort mode there is a bit of a pogo effect/bouncing, which is only noticed on few occasions such as very small speedbumps when going over them at a decent speed (due to this sport mode is actually better for small speed bumps).
And on some roads the undulations dont do comfort mode any favours and you can feel the bouncing although its liveable.
I have been thrashing my car a lot since getting the suspension done yesterday, its all been uneventful except for 1 time it felt as though the whole car was sliding around a bit and I instinctevly was wobbling the steering wheel to straighten it up, it felt very strange, there was no tyre squeel and TCS did not flash. I will try repeat this again on the same section of road.
I cant comment on the handling because I dont push the car to its limits handling wise, but I have given it around some twisties in both modes and there was no funny business.
I will update when I try recreate the weird sliding sensation of the car. And also when I put on the PSS tyres.
Here is the only other review I could find for the specific suspension:
http://www.e90post.com/forums/showthread.php?t=270940
Also I contacted Bilstein and they said this suspension was for both runflats and non runflats.