When doing a multi-step mash, does the amount of time you take in between steps to raise the temperature make a difference? (Aside from the obvious "taking longer will make your brew day take longer"). I've only done multi-step mashes a few times. The first time I basically had my burner on the whole time and let the mash temp raise from about 120°F to 152°F over about the course of an hour. The second time, I let it rest at each step without any heat and heated between steps as quickly as I could manage to stir without scorching. Raising quickly certainly takes less brew-day time, but I can't say I noticed any difference in the final wort (disclaimer: these two mashes were not the same grist, so it wasn't an experimental comparison, so to speak).
Is there something happening on the enzymatic level that I'm not aware of? Does this make a difference only when using under modified grain?