In February I traded my 2002 E39 540i for a 2012 550i M-Sport. No regrets whatsoever.
The only downside I notice is maneuvering in tight spaces and parking. That's when the car feels big to me. The top-view cameras help somewhat. Around LA, I tend to avoid all the tiny parking lots and park on quiet streets a block or two from my destination. This also avoids door dings and makes me exercise more, possibly adding a few months to my life expectancy. See, it's all good.
Once the car gets going, it's so quick, solid and nimble that I don't notice its size at all. It feels far more powerful than my 540i. I am not one of the people who is disappointed in how communicative or responsive the steering is. I just love driving it.
One big plus I didn't realize on my test drives was how much more quiet the interior is. When it's time to creep along at 3 mph on the 405, the car isolates you into a peaceful bubble away from the stress where you can appreciate the subtleties of some quiet classical music. When you finally pass the ladder that's blocking a couple lanes of traffic and gun it, the engine emits a satisfying snarl and you're back in a race car again.
All the technology is wonderful. The Executive Package includes HUD, right? You'll definitely want the HUD. I turn off the navigation's voice prompts and just watch the magic arrow that's superimposed over the road. Makes nav far less annoying.
I loved my 540i for the seven years I drove it and was very reluctant to trade it in, but I'm so very glad I did. I believe my 550i is my favorite thing I've ever bought.
Current: 2012 550i - Jet Black - Black Leather - M Sport
Retired: 2002 540i - Jet Black - Black Leather - M Sport