Interesting points said here in this thread, but lets shed some more facts here in regards to the 1M and the M3 as it seems there are a ton of 1M fanatics here.
The M3's S65 motor is worlds apart from the N54. I have owned 2 335i's, fully modded, it doesn't hold a candle to the S65 as far as sheer driving pleasure and response time. If we are talking about track performance, the N54's response time is very sluggish compared to the M3's S65. The S65 is truly a work of art, anyone wanting to deny that, well, is in denial.
Again, more on track performance... I (along with many others) have been consistently capable of throwing the N54 into unfavorable temps to the point where it hits limp, on the street. In a track environment, even all the additional cooling done to the N54, it is still a turbo car, it still has CAST turbo parts that will become very hot and will always run hotter than the S65. BMW should have help vent the new 1M more for expelling heat, they didn't. The S65 has a pure equal length Stainless Steel Exhaust manifold.
Handling.. The 1 series chassis is greatly the same as the 3 series, except BMW cut off most of the SIZE of the car off the rear. It upset some of the balance of the car, drive a 335i and a 135i back to back, and you will soon realize the 335i has LESS understeer and feels more balanced, even though its a tad heavier.
Engine placement and weight balance. The 1M/135i is a straight -6. The M3 is a V8. Inherently the V8 is shorter in length, there is less weight hanging over the front subframe. For those wondering, this is not an assumption, I have actually measured the differences.
Please compare a 6-Speed M3 to the 1M, not the DCT. The 6-speed M3 variants are not bad on weight compared to the DCT variants. Go weigh in a 6-speed MT M3 on scales, and see how much it really weighs. My M3 weighed in less than my 335i coupe did. (personal experience)
Before calling the E92 M3 a porker, please look how heavy the Nissan GTR is. Does it magically defy the laws of motion? No.
Will the M3 continually be better than the 1M after the 1M is released performance wise, I personally think so. Time will answer all these questions and doubts.
Is the 1M a great car? Yes it is. It has to be, it has most of the M3's underpinnings.
Is the 1M worth its price? Yes.
Would I buy one over an M3? No.