I have my 2013 M Sport now, ordered at the end of November.
I ended up with the All-Season tires option (which supposedly wasn't a choice yet): 18" Pirelli Cinturato P7 All-Season Run Flat (different tire than the Summer Pirelli Cinturato P7 Run Flat).
The wheels are non-staggered, so 225/45 all around (just like on the F30 M-Sport all-seasons). This likely means I don't have the increased top speed limiter (not a big deal as I should never be driving this baby hauler that fast).
Ride is very comfortable (especially for run-flats), but grip is a lacking a bit compared to the performance summer tires I'm used to.
The square setup should reduce understeer vs the staggered. I plan to remove the run-flats once they wear. I'd like get a bit more rubber and fit 235/45s. Plan is to fit Michelin Pilot Super Sports (best tire I have ever owned...transformed my E90 335i) and keep a donut in the boot.
....not sure if I will rotate the tires or not. I just want to get to the Pilot Super Sports ASAP.