Let me add my 2 cents:
There are some in this thread who actually "get" it, and there are the typical American car owners who say "I can spend half as much as that and make my car go just as fast." Every once in a while, you have to lift your head out from the mud and muck and take a look around, or the world will pass you by.
Like a couple of people said, yes you are paying 50k for the car, but you're getting the total package. I never realized how much of a pile of crap (build wise) my mustang was until I got the 335. It's literally "night and day." Don't get me wrong, my mustang was more "fun" to drive and it did handle better than the bmw, but there was some serious
suspension work done to it so it isn't a fair comparison. It is more comfortable, faster, quiter, built better, stops/brakes better, yadda yadda. You also have to remember that within that 50k purchase price is 4 years of FULL maintenance and warranty work, ALL inclusive, zero out of pocket.
Am I biased? Maybe, but at least I can give everyone a FAIR opinion because I own/owned both, so it isn't an opinion from someone only on one side of the fence.
The link one member posted was an old article about the Vishnu Procede, most likely the first generation of his incarnation. He's on the 3rd right about now, and flashes are on the horizon that will change the playing field. Currently, there are only 2 or 3 flashes available, but those require you to either send the ECU away, or pay Dinan with your first born. The game will change in N54 tuning very soon.
Take a minute to look at dragtimes.com, and look under "search," then "Bmw," then "335i." You will be in for a very unpleasant surprise. The current fastest 335i ran an 11.829 at 117.91 with (I believe) a piggyback tune (550 bux), maybe downpipes, an exhaust, dual cone intake, and DR's. That is fuggin fast people, pay attention. The best part about it is that they can be a total sleeper. You pull up to a stock-looking one, and he/she may just be idling quieter than you can hear. Maybe they even have an exhaust to add a little mystery to the equation. But once the turbos spool up, there's almost full torque at 2k rpms.
I still love mustangs, and I will have one again one day in the future, but don't be naive people in regards to what you don't know about or what you can't honestly comment about. Both are great cars, but they serve TOTALLY different purposes and are meant for two totally different MARKETS.