1. "Continue approach, you're number two with a 737 to depart in the gap" provides, I would suggest, situational awareness to both the inbound and outbound traffic on frequency, without using the phrase "line up".
2. I was surprised to hear some positive comments from some crews after the suspension of conditionals at a biggish airport some time ago - more than once they felt it removed any ambiguity, and left them merely with the choice of "hold position" or "cross runway xx". I had expected everyone to claim reduced situational awareness but that didn't seem to be the case.
3. Ultimately it boils down to common sense - there are times when conditionals are extremely useful, especially if you can let a heavy adjust their speed to continue rolling or minimise line-up time. But I only need to use them occasionally, and there are some crews (no names / nationalities here) that I wouldn't dream of using one with, especially having witnessed a nasty incursion as a result of a conditional clearance being misunderstood.