Personal preference. I've seen it done both ways, and used both ways. I think if you are going with the 12" spread, in an arc is fine. If you are going in only a 4" spread, then do them straight.

They are 8" spreads, actually.

My personal preference is to follow the curve which is what we did with our 8" spread faucets. It's pretty slight so I'm not sure it's very obvious in this picture...

It's going to be more noticeable on a smaller sink, given the smaller radius of the curve. It's the right thing to do IMHO.

I did pillar faucets on my small (tiny) basement sink and had them drill the marble following the radius of the bowl.

I guess I always just see them in a line in the showrooms so this seemed odd to me. I'm going for as much of an historic look as possible--doing them curved is in keeping with that?

Has anyone done the curved spread with a Kohler Caxton sink? MY granite guy didn't even ask, and when I requested in the final vanity (others too late) I was told they couldn't do it because of a flange on the sink. Disappointed because there is sooo little room between the faucet, handles, and backsplash.

Follow the curve. It makes the handles easier to reach.

I need to replace a faucet that was installed along the curve of the sink, with an 8" spread. Is there anything I should look for in the faucet to make sure it will be ok to install on the curve as opposed to along a straight line?