Goodness, guys! It's used for separation for guys on the straight in for 25L! I just always tell them each time they slow me down "we'll slow, but is it okay if we're high?" 99.99% of the time they'll say "approved" and then just hit FLCH, dial in the slower speed and sit back and relax as the airplane first slows down while going above the VNAV path. Then you're coming down at your nice slow speed as fast as the airplane will allow in that configuration. Hard to hit wake turbulence on the arrival when you're above the guy in front of you.

As for the base-to-final turn following someone who's a straight-in in front of you, it's just a matter of situational awareness. You can see him visually or on TCAS (I haven't seen a plane where TCAS was MEL'd... yet) . Worst case scenario, you hit the red button on the yoke and show everyone else on board those sweet flying skills you've honed over the years.