I have had a couple of E9 BMW's, still have a 2007 with 130k on it. The older ones with hydraulic steering drive great. The newer ones with electric steering, not so much. But I have not driven a 2016 up. I find my 3 series a great driving car, and still like driving it. But I have other cars to drive. To keep some miles off of the BMW, it is garaged in winter. Coming from Toyota's, my advice is to lease or get a CPO with a warranty. If you are going to buy, follow Mike Millers service advice. My E9 at 100k needed a valve cover gasket, oil pan gasket, and oil filter housing gasket. The gaskets seem to be made out a rubber that takes a compression set, then leaks to the point of annoyance. I have done 2 VCG gaskets on my present car. Don't let the oil filter housing gasket drip on the serp belt. More expensive problems will result. The 100k service should include plugs, trans fluid, etc. Not cheap if you have someone else do it. LL-01 motor oil OR what BMW calls for depending on year and model you get. The A/C compressor went out at about 115k. The water pump is electric, and not cheap. They tend to fail suddenly. Look it up. Control arm bushings at about 115k. Yes, and you do have to register the battery. Most are AGM. Again, not inexpensive. Runflats, I have used both non-runflats and runflats. I presently have Bridgestone Driveguards, a runflat, not a performance tire, but they are not harsh at all. A good all season tire. The shocks are junk at 60k IMHO. I replaced them with Bilstein and never looked back. HVAC motor failure, replaced in about 10 minutes with an inexpensive aftermarket unit.
They are nice cars with great aftermarket support. Think FPC Euro, ECS tuning, Bavarian Autosport, Turner, Bimmerworld. If you plan to keep it after warranty is up, you best be a good at doing it yourself. Finding an independent that is good and who won't break you wallet is not always easy depending on where you live.
Just go into it with eyes wide open, and be prepared. They are not Toyota's/Honda's, and that is a good thing if you like driving BMW'S. I drove mine from MA to AK two years ago. A great road trip car. Only problem was a punctured Conti run flat in Palmer AK.