Biggest downside is that the cockpit is now Garmin Gx000 instead of Proline 21, but that is presumably the main reason they got the price down.
I'm not sure that IS a downside?
I've flown King Airs and CJ1s with Proline 21. I've also flown Garmin G1000 - most recently in a brand new Caravan with the synthetic vision option and I'm a HUGE fan.
In MY opinion the G1000 is a whole lot nicer to use than the Proline 21 and the 'M2' is getting an evolved version (G3000 rings a bell?) which I reckon will be an absolutely cracking bit of kit.