A guy who just recently left where I work has a new Model S performance Tesla in that dark grey color. Awesome car. He took me for a spin and let me drive it for about 15 minutes a few months back. Truly is an impressive car. The speed is deceiving, as it feels like gliding with its near-silent operation. The 17" screen that controls all functions is pretty great too.
I haven't been in a new 5 or 7 series, so it's hard for me to make the comparison. My only complaint about the Tesla was I would have liked to have seen just a tad higher quality material on the interior given the price. A suede steering wheel and perhaps some accent stitching would have been that little extra touch. I'm being nitpicky though, as overall it was very impressive.