It's all in the mind. I used to own an Accord which was very similar in size to the E60. But I parked it anywhere and everywhere I liked without hesitation. But now I find I think twice about where I want to go before deciding which car to use. If it's to a place where I think it will be "difficult" (e.g. tight parking, lots of cars double parking, etc), then I take the 325. The 530 seems so much bigger in terms of the tolerance level I am willing to put up with. Gaps where I would just rush in with the Accord, I now think "can I make it?". And you know once you start to doubt, all is lost.
So it's more of fearing to scratch and dent the car more than the actual size of the car. Maybe this fear will go away once I've had the car longer.... or after I get a 7-series!