Yea I've noticed this as well. The only thing that seems noticable is Letho being there or not.

Ioverth isn't even in the game.... neither is Saskia with little to no mention of them.

Roche and Ves treat you the same no matter what.

Is Sile in the game at all if you didn't kill her? No idea on that one. Probably just a mention though.

Would be nice if CDProjekt would release the exact differences that can occur. Seems like the only main physical differences are Letho and the Tattoo.

What I noticed: Letho could be dead or alive, depending on end-game decision, and judging by list of offered saves, game grabs data from before confrontation with him.
Also in my save Nilfgaardian told me that Henselt was dead, as I let Roche kill him. No other differences noted so far, Heard that Sile may be in game as well, but haven't seen her for obvious reasons. :)

She is, but only very briefly.
Letho, dead or alive is the only one that makes a difference.

Yeah, the sad thing is that I removed my tatoo in Witcher 2. But now it's back.

Truth be told, most characters are seen rather briefly, with very limited interactions, sadly.

He's dead no matter what you did. I tested it out with a save where he lived and the Nilf's still said he was dead. Probably from the fight against Radovid.

Yeah, but I mean the way it is said. Friend of mine told me that accent changed, unless I misunderstood him - we were both falling from our feet. :)

I've barely been able to tell that I imported a save... A part from what I've heard that you encounter Letho at some point if he lives it sounds like people who took Iorveth's path into Witcher 2 for instance are going to be really disappointed.

With barely any noticeable decisions taken account of at all. I guess decision making really pays off in Witcher 3 itself but still a shame that there isn't that consistency.