I've been running a small case lsd with a 3.45 ratio in my M44 engined 318is for the past few months. It was an lsd that Valdas fitted to the differential for me back in May.
So far I've found it to be a nice improvement over the standard diff. Most of my driving is motorway based and so the engine is revving slightly higher than standard but nothing major.
I'm running 245 wide rear tyres and the car does feel a lot more planted but it can still brake traction if you want it too.
Overall i'd rate it highly for daily driving