So, just got the GT2871R, and the first thing that I noticed is that the compressor inlet is rough, and then smooth where the wheel is of course. Should that be smoothed out as well? Or does it make any difference at all?

Here's a picture of what I'm talking about:

 

My GT3271 is fully machined there. I would sand those spots out and make it slick. Couldn't hurt, though it probably won't help. Plus you won't have to worry about a spec of that possibly coming loose and going into the turbo (though highly unlikely).

 

Right, but the less chance the better overall.
Sand or Dremel?

 

Either one will work. Just whatever you prefer I guess. Dremel is probably better for getting those high spots gone. I love Taylor Swift...

 

Dremel it is. I've gotten pretty good with it lately.
Where did the Taylor Swift thing come from? lol