I am a die-hard BMW fan. I owned a 328i before and currently an X5. To me BMW delivers the ultimate driving experience. It is definitely not the most luxury or exotic car, and it is underpowered by even some of the Japanese models at the same price range. However, the combination of handling, accelation, braking, and stylish design makes it the no.1 mass-making sporty luxury car.
I highly suggest everyone who is in the market for new car to consider test drive a Bimmer, and you won't be disappointed.
Regarding maintenance charges, all BMW has a 5 bar indicator that tells you when the maintenance is due. I have driven my X5 for 8000 miles now, and I still have 3 bars left. So it is very normal that you change oil every 12 monthes.
I like M-B also, but i think you need to move up to at least E-class to get the MB buld quality and comfort. My favorite is the SL series, but the price tag is way beyond my reach. The C-class is really poorly put together. The M-class is also a bad example. The rear looks like a van.
I personally don't care too much about Audi or VW. The interior design feels girlish, and resell value is poor.