I recently installed these on my 2006 320SI. The 320SI comes stock with the m-sports suspension and in europe the m shocks costs about the same as the B6 adjustable 10's. My m shocks were worn and needed replacement so i figured I would try the adjustables. I take the car to the track from time to time and recently I drove it on the Nürburgring.
Overall I am very pleased with the shocks. They handle uneven roads better than the stock shocks and have really made the car a lot smoother. The adjustability works just as advertised 1 click either way is clearly noticeable.
However I suspect that the shocks have been valved for the stock suspension springs since i have settled on a setting of 8 for day to day use and full on 10 when riding on the track. I had hoped for a slightly more aggressive setup . If you plan on running harder lowering springs I think the dampening will be inadequate. (B8 adjustables would make more sense imho.)
It's also worth noticing that the gas filled bilsteins provide some spring effect themselves and the ride height of my car has actually increased about 1 cm. To compensate I am considering a set of eibach pro's (or is it sport line? I forget... the softer option anyway.) This of course means removing the struts again - which isn't so easy on the e90.
If you are looking for a replacement for stock or msports shocks and your primary objective i getting the day to day ride just perfect i would highly recommend the b6 adj. However I personally would shell out the extra cash and go straight for the B16 PSS10 coilovers if I had to do it over again.