I have my reasons, and one of them is in your sig picture...
I had an e39 as well. I still on the E66 but will be getting rid of it soon.
It's about bottom line for BMW. They make a (relatively speaking) inexpensive luxury auto (compare to true luxury brands thtat have been around for much longer like Bentley). How can they do so? Make money after the sale. Even if you have your warranty with your new BMW, you'll still spend 15K+++ over the next 6 years on repairs that are routine or not covered. Parts, repairs and maintainance is basically pure profit (oil change - $250? hah, break rotors: $1500? hilarious). So BMW sells you a car made with cheap parts that will break for cheaper than the competition (and cheaper than last year), knowing that they'll make it back later. Don't you wonder why cars keep getting cheaper in a world where everything is getting more expensive? How is that possible? Simple: cheaper parts (of course there are other things like economies of scale and automation). and yes, even if you car is new, it's going to be in at the dealer all the time. Do a quick search on their new cars and you'll cringe at the stories of how many times people have to go to the dealer within a week.. Or you can just go visit the local dealer and watch the cars line up down the street to be fixed.
BMW are not the only bad guys here, they are just an excellent example. Don't get me wrong, I love their styling, the engines are bulletproof, and are a blast to drive. BUT I would not buy another one because I do not like the way they do business. I'd rather pay the premium for good parts up front than wasting time at the dealer later on, even if the repairs are covered. The solution? Buy a Japanese auto. You will say "oh they're just the same" but have you owned one? do you know that? I've owned a number and they have all been better than my Audi, Porsche and BMWs. The downside: you lose the exclusivity of the luxury german auto. However if I may I would add that BMW won't likely be exclusive forever, since their goal is mass production (2 million cars for 2012), and with the introduction of the cheap new "i" line. Essentially the brand name will become diluted, sadly. Or maybe the other option is to buy a Bentley. I don't see many in at the dealer for repair, and they are rumoured to be built to last for 100 years, but not having owned one I can only speculate.
As with you, just my 2 cents. My analysis is certainly based on facts and experience, but that does not make it true for everyone. Maybe I have been the unlucky one, and everyone else has had a great time with their bimmers like you.