Would it not seem more readable to have the second argument as it currently stands:
$query->where( 'field.a = 1', 'OR' ); $query->where( 'field.b = 2' );
Changed to be the first argument:
$query->where( 'field.a = 1' ); $query->where( 'OR', 'field.b = 2' );
Also have it a *requirement to declare the operator in the first argument of a where() method following another. This seems to be more logical to me. Also when the sql in the first argument is long it can be easy to miss the addition of the operator override...
$query->where(array ('field.a = 1' ,'field.b = 2'), 'OR' );is also an alternative.
No I don't think it's particularly more logical to have it first especially since it is optional both because sometimes you have only one condition and because sometimes you are using AND and just want to use the default. If you put it first you would have to deal with it all the time.
Elin