"It's called DTC but it should be called fun," says the Autocar reviewer in the video. "The car will come out of corners like a proper rear-wheel car"
Limited Slip Differential or LSD is something that can be had on the //M3 but not the 335i, that is until now. Dinan sells a version for $2,595 (comes in two versions one for Auto and the other for Manual transmission.) Another manufacturer Quaife is selling their LSD for $1,305, that's a special price on the E90Post board.
So why even get a LSD for your car? Limited Slip Differential is designed to provide power to both wheels instantaneously allowing for faster lap times, better control and even power distribution. Most will feel the advantage if they track their cars. For thosee who do not track their car they will see some advantage when roads are rough where the LSD will correct the impact of one wheel hitting lumps and bumps on the freeway without having the pounding we feel in the open differential that is in a stock 335i.
You can learn more about Open vs LSD differentials here.