I don't like the way it looks on a single record form so I normally turn it off. But, my apps rarely have record contention so there is little chance of both userA and userB attemptiing to update the same record at the same time. Most records are updated based on some client interaction and the client wouldn't be talking to two users at the same time
However, if you might have contention, leaving the record selector visible gives you a warning that some other user is updating the record. Normally it just shows a right triangle but if you type something to begin to change the record, the right triangle changes to a pencil. Or if two users are looking at the same record and one starts a change, the marker on the second user's form will turn to a circle with a line through it.