More on the 'high end' of the PHEV spectrum; 20 EV miles; they sold 10 last month so perhaps at least worth a mention ... plus that odd placement of the charging port (in rear bumper) is the same as the C350 but of course at a higher price level; not exactly hidden but perhaps a throw back to when cars used to have their gas caps under the rear license plate! (yes, they actually did!). Also a full road test by CNET embedded in this article.
I went through MNL and did a search for S550 plugin and saw no thread; if there is one feel free to merge this one ... lots of comments on this approach by MBZ
Here is another photo, this time of the C350 PHEV with the charge port in use; lots of styling similarities ... rated for 19 EV miles but I'm sure that will vary; S550 has a bigger battery (8.7 kWh) versus the C350 (6.2 kWh) but of course more weight, etc.