Talking from a standard driver, I have gone from a 235 to an M2, the difference in driving is noticeable, road handling is a huge difference, acceleration, even though I cant go above 5k at the moment, it is considerable.
The sound, well you dont need the internal electronic sound, the sound is enough that it brings a smile each time i put my foot down, or dropping down a gear when using manual selection, that... well i have a box of tissues to wipe up my drool.
I have the DCT, and the gears change rapid and they are so smooth.
Inside not a great deal, a 235 with a few M features, however the seats feel softer and more comfortable.
If you can afford to upgrade and that's what this is you wont be disappointed.
This is just an honest opinion from a bog standard driver
who finds any excuse at the moment to drive it, i find my self thinking of things to go and get from shops just to get in it.
As you can tell, loving it