I agree with the previous posts. A little more justification for the answer please.

Also, I'm sure that I've seen my execution plans change

WHERE colA IN(1)

into

WHERE colA=1

and

WHERE colA IN(1,2,3)

into

WHERE colA=1 OR colA=2 OR colA=3

Though to be honest, I can't replicate that right now. I might have seen it running a trace at some point.

It does highlight how SQL tests a value in 2 columns though:

WHERE 1 in(colA,colB)

turns into

WHERE 1=colA OR 1=colB