Hello,
I am a new member but have owned my 2002 745i for over a year now. In terms of reliability I think the car is great mechanically....software wise it is a bit buggy. I've had my software reloaded/updated by the dealer at no cost but buyer beware! I would not buy one which is not a Certified Pre-owned. If the vehicle is certified the dealer is more giving when you have problems. I believe that one needs to spend a little time to get acquainted with the I-drive system...other than that it is not difficult at all. Just think of the I-drive control as your mouse to the PC/Car. My brother drove my 745i once and loved it.....he will be getting his 2007 750li in a few months.
Good Luck,
Wayne