I have 53k on mine and haven't had any serious significant issues. Because mine was a grand touring the wheels began to peel and Mazda paid to have them refinished, so they're like new. Some owners have had issues with the brakes becoming warped or shuttering around 30-40k miles, but mine have been flawless because I commute in the vehicle and brake easy (it's not a race car!). The maintenance cost is low, but you want to use the mazda OE oil filter on it if you do the maintenance yourself - but it's $6-8 unlike your BMW filters. The transmission is sublime for an automatic, and you'll get used to how it holds gears instead of overdownshifting.
What you'll find if you're like me is that 184hp is enough for everything, and you'll coast very long and into the backs of other people if you hypermile. You'll love that it turns 1500rpm at 50mph, quiet and effortless for a 4 cylinder. You'll want to go on road trips because you'll average 34-38mpg on trips. The fuel tank is huge for the fuel economy, so 450-500 miles between fuel stops is normal! Lastly you'll love the maintenance because it's nonexistent in terms of cost. If you do get a light color interior it will wear faster than you may like, but use plenty of leather conditioner and it will hold up well.
As for maintenance I do oil changes every 7500 miles by the book with 0w20 synthetic, and use OE filters, and my running costs for maintenance including a new set of tires at 25,000 miles has been under $0.02 per mile. I recommend doing the cabin filter yearly, they get dirty super fast on these cars, and for $15 it's worth changing. Also you should get apple carplay in the future as they are going to introduce an update for cars back to 2014 that have the connect system, so give that some thought and hope.