Ok, so I won't be posting pictures of my new rims tomorrow.
Turns out the smart service center in Buffalo (which is a Mercedes dealership in sheep's clothing)
didn't have tires that fit the new rims. This, despite the fact that I emailed over a link to their department lead a month ago and specifically asked to make sure they would have tires for them... and he said they would.
And I can tell you, the stock all-season tires do NOT do well in the snow. I drove trough a bit of snow to get the service done, and it wasn't fun. I'm hoping the snow tires are better. (It JUST snowed here for the first time since I bough my car.)
Needless to say, I'm not pleased with the service center right now.

In retrospect, it's probably better, since new rims are an inch wider than the stock rims, both in front and in back. Meaning they would be better suited for summer tires anyway. But it still doesn't change the fact that I have a set of new rims with no tires, which will be sitting in my garage unused for the next 6 months. All because my smart service tech can't be bothered to read his email before verifying he has parts.