Hey guys, just wanted to say hi! First post, first mercedes (had a plethora of lexus', infiniti's, bmw's, etc). I've already been active on forums for the cars I've had and this seems to be the premier MB forum.

2008 S550 4Matic, Silver (not sure what the MB term is for it, but your stock silver color).

So what do you guys do to these cars? I've had G35's, G37's, M6, all cars you can play with, but this seems to just be a supremely luxurious ride (first 4 door car too).

First of all welcome. I think that most of the S owners pretty much keep them as purchased without too many mods (I know there are quite a few posts about mods here). While I know that you can DIY on your S, it is not an easy thing.
Michael in Arizona

Welcome, nice ride.
As far as performance, you can’t do too much. Just filters and ECU tune. S class isn’t a big market when it comes to performance parts so no company wants to waste time and money creating products. You can always do a one off custom build with a blower or a turbo if you really want to get more power.
If you want handling, lowering it a little and strut tower brace will improve handling, but has a potential making it stiffer. However, coming from a BMW you probably will still think its soft
Visually, sky is the limit just like any other vehicle.

Welcome to the forums!!