Just picked up the 2015 CM (s-model) and a few quick observations. Identical in performance to the 2013 model. Dealer mentioned it may get a little better gas mileage but have not had it long enough to verify.
Only 2 things pop to mind while motoring- the volume controls in the steering wheel have much better feel when pushing in. The 2013 felt mushy and you had to keep pushing on it to raise volume. 2015 no issues. Also the window buttons in the door appear to have been moved slightly forward. I like them better now they seem to align better with my hand so I hit the front button all the time on first try. Also dig the black button to open doors without using ur key fob.
Cosmetics- there is an "s" on the front now and the wheels have a slightly different design.
I had regretted not getting the auto climate control in my 13 but this 15 has it and I am so glad. Set it and forget it. In the old car always seemed to fiddle with the controls to get it just right.
For those that wonder about the maintenance- in my 19 months with the 2013 I had "0" issues. I purchased the car as a nervous wreck hearing bout the problems folks were having and looking back never thought once about maintenance. Great service at my dealership and actually is my #1 selling point with Mini's. I drove the heck out of my car and had 42k miles on it (19 months)-when the dealership announced an upgrade program. I was over the 3yr/36mo warranty and decided to jump on the deal. So far happy as a clam and back to no maintenance costs for 3yrs/36mo. Oh and I think it comes standard with the flat floor now. love it and you can stow some things underneath and still place ur luggage or groceries on top of the flat part. All in all so far happy with the upgrade. ( I hope they have fixed the fuel tank where u have to continue filling once the shutoff valve on the gas pump shuts off. I hated that.

 

I thought it was just me, but now that you mention it, my 2014 CM does the same thing.

 

Good to hear, getting ready for the end of our '12 lease...headed to a '15 as well.

 

@TJTank- no you are not alone. If you search back to 2012-13 you will find much mention of this. Generally you could add like 1-2 more gallons after the shutoff valve clicked at the gas pump.
The first time I ever filled up- the reading on the set/info area said 397 miles. Since then I have never got that high of a reading. Mostly 365-375 reading. Interested to see what happens with the 15 model.

 

Now I'm really contemplating on getting a 15. Lol! But I've done so much work to mine. It almost can be mistaken for a '15.

 

If you turn the gas nozzle upside down it doesn't shut off till you are actually full

 

I dunno about the auto climate controls, meaning set it and forget it.

I set it where I want it and the girlfriend keeps mucking with it up or down because she wants colder or warmer air blowing on her. Then when I get back in I have to set it back to where I know is just right.

Maybe in '16 model they'll let me set a pass code lock on it

 

No kidding....I gotta try that on my first fill up.

 

Oh I hate it for you man....My wife doesn't like to drive it ....to much horsepower so I have no such problem. She doesn't even want to know what the settings and controls which is fine by me. Giggle!!!

 

It's all good life is sweeter for her in it.

Enjoy the heck out of your '15.