Do you guys "rinse" the yeast cake prior to repitching or just rack the fresh wort onto the yeast cake? I tend to "rinse" the yeast but am wonder if this step is really worth the time...
IME, no, it's not.
+1. Tried it both ways, and there was absolutely no difference in the quality of the resulting beers. So for the last 20 years (at least), no rinse.
I do tend to reuse the yeast cakes (stored in an jar or flask in a 34°F fridge) within 3 weeks or less, so I can't speak for whatever advantages rinsing may
have for yeast which needs to be stored longer. If you switch off and use lots of different strains and the yeast cakes need to be stored longer, it may be a different story.
But if, like me, you primarily use 1 or 2 strains for the bulk of your brewing and brew fairly regularly, the rinse is unnecessary...even through multiple repitching.