I've had a late 2014 (so it's pre-facelift) AWD Sports Nav auto for about 10 months. It returns about 40mpg, maybe 45 in summer if I'm really light footed. I previously owned a 2015 (so that one was post-facelift) Mazda 6 Sports Nav auto, and we also have a 2015 Mazda 3 SE-L petrol auto.
The auto box in all of them is great, and it changes gears predictably, quickly and as expected. The 'creep' works well, and holds against any hill-start I encounter in normal driving.
After the first couple of thousand miles I swapped the 19" wheels on mine for the 17"
wheels from the lesser spec model winter wheels - the ride is quite a bit softer, road noise about the same, steering a bit heavier, not quite as much road feedback but still more than enough. Personally I prefer the the softer ride and I'm sticking with the 17's.
Spec wise, I could get by with the 2WD SE-L, and I reckon the only thing I'd miss is the heated seats and the dimming rear view mirror (unless that's included in the SE-L). I'd maybe miss the keyless entry and the reversing camera a bit. The self-turning headlights are only really of any use on twisty B-roads (but they're xenons so they're really good, they shine further than the LED's in the 6 although the LED's are brighter), the Bose system isn't that great (the one in the facelift 6 was really good tho), I prefer cloth seats in a car, and small things like all windows having one-touch opening I can live without.
Mine also has the safety pack. The auto dipping headlights are great on A/B-roads, but on motorways I often still need to dip them myself, plus they don't switch on high beam if the screen has some steaming up inside or some frost on the outside. The lane departure system is a bit annoying since my commute is in the middle of the night on completely empty roads and it beeps at me for not indicating when joining a slip road etc. I'd probably switch it back on for a long motorway drive if I was tired tho. The blind spot monitor only works if the car approaching from behind does so at a speed reasonably faster than me so it can't be completely trusted.
It's a great car to drive - I find it very comfortable, the high seating position gives a great view and seems to be a bit above the glare of oncoming headlights. SWMBO also loves it, even tho she didn't take to the 6. There are quite a few horror stories around on the diesel engine tho, and I wouldn't own one out of warranty.
Hope this helps