OK guys, I have not been too active on the boards for the last two months, but would like to chime in on my impressions of my 135i after deciding to keep it for awhile...
The build quality: My main concern with going from Lexus and Porsche. I must say that I am actually disappointed with the overall feeling of "solidness" of the car. Lexus is definitely a much better built car, and Porsche is still much better as well. The car seems to lack the feeling of confidence in reliability and driving feel of quality.
The Engine: This is the best part of the car by far, and is very fun. I currently stock ( I am going to buy another JB3 or CP-E Standback), but the engine is very exciting, and the tone is great. This does not come without flaws, as the car does sound bad at idle when cold, and I have low RPM misfires that I am going to take it to the dealer for at 13k miles. With boltons, the car is an animal ( I was making 384 RWTQ on a mustang dyno with just RR intake, JB3, and Remus quad axle-back exhaust on a mix of 91 and 93). I am sure I was making over 400 with the RR downpipes, CP-BOV/hardpipe, and 93 on map 5.
The transmission: I had very mixed emotions from the beginning. It is pretty notchy and sloppy, and definitely not the best for a car of this caliber. I added the BMW SSK and CDV mod, and while it is better, it still leaves a lot to be desired for the reputation BMW has for silky smooth drivelines. It couldn't hold a candle to the 550 edition Boxster S I had before this car.
The suspension: I can sum this up pretty quickly: It Blows. It is very nervous at high speeds, and leans like a 1970's muscle car. This will soon be taken care of with KW coilovers, and with my front sway bar I already have. I would recommend this to anyone buying this car as the sport suspension labeled as an ///M suspension is a joke.
Wheels/Tires: the wheels are fine for stock, but the run flats suck as it rides poorly, and is overall way too stiff. Replace them with something else when you get new tires.
Logic 7 Stereo: It is definitely a great stereo, and much better than any Bose system than I've ever listed to. It is not near as good as a Mark Levinson or Nakamichi, but I am happy with it.
I-Drive: The least user-friendly Nav system/ Car control system I have ever used. Stop cheaping out BMW and get a dash integrated touch-screen system like Lexus.
Comfort Access: I would pass on this option if I built the car again as it is overpriced, and can sometimes not allow you to unlock the doors without removing the key from your pocket.
Overall: The car is very nice, but BMW needs to spend more time on suspension, and options development. They also need to put in place a maintenance program that that will keep your car in good shape if you follow, instead of pushing a crappy one and advertising free maintenance. It's disingenuous, and I hope nobody actually waits 15k miles to change oil as it will damage your engine in the long run.
Thanks for reading, I know it was a long post. I am trying to be as realistic as possible, and not hype up a car simply because I own it... That does no good for the community/ prospective buyers