I've only done a couple track days so far in my M240i. I bought it for use as a daily, and to take a break from spending big bucks tracking my C7 Z06. Overall, I'm pretty happy with it. The powertrain is fantastic. I've never tracked an auto or DCT before. With this being a car for my girlfriend to drive also I chose the ZF auto. I've been manually shifting and 3,4,5 are great on the track.
The understeer is tough to deal with but expected. I've added M3 control arms & tension struts (Only $400 via Rock Auto) and that helped. I'm at -1.8/-1.9 camber up front, enough that I don't completely destroy the outside edges of the tires. I don't want to add camber plates for NVH reasons, so tire size is pretty limited. 255 on a 9' wheel won't fit, and that was my original plan. Looking hard for my next set of tires.
I don't have plans to add LSD either. I think that modding the car to that point just isn't cost effective. I think if a good deal for an LSD would come up I would rethink it. But why not just buy an M2 or M4 in the first place?
If I were purely hunting lap times vs $$$ I would buy an SS 1LE. They are just an unbelievable bang for the buck. They have the magnetic shocks that the C7 & C8 Corvettes have. The shocks are magical, car is set up great for the track. I also agree that a Cayman looks like a fantastic car on track. Prices are just crazy now though. A director at my company just bought a GT4, looks great.
Driving the M240 close to stock on the track seemed pretty disappointing. Then I watched Randy Pobst tear up Streets of Willow in an M235i. He's just amazing. I can't wait to get back on the track again.
Video of Randy on track is embedded in this article. He goes on track at 6:40.
https://www.motortrend.com/news/2014...t-on-ignition/
Edited to add: I was way too critical for being a newbie. I apologize to all who have spent the money on an LSD. There's no doubt that it take's a big step towards making this a real sports car. It just sucks that we have to pay $3K for something BMW could have done for under $1k from the factory. If they can paint our cars beautiful racing Estoril Blue and put 16 "M" badges on it, why not add LSD? Mustang, Toyobaru twins have them, C'mon it's a $50K car.