You know, I had my rear passenger side regulator fail twice on my E46. The first time the car was still under warranty so no cost. The second time, the car was no longer under warranty, but the regulator had been replaced less that a year before so they did it again at no cost.
However, a few days ago, I went on a test drive with a guy who wants to buy my car and the front passenger failed - how embarrasing!!! He still wants to buy (thank god) but I had to call BMW to see what it will cost and it's $250.
I'm glad it's not just me having these problems - I've never had a regulator fail with my other bmws.