Well, I'm not a pro, which means you certainly know a lot more about this than I do. Anyway, here's the story. I'm looking at an FZ20 or FZ5 to replace my trusty and old (but also heavy) Olympus IS3000 that died recently. Actually, I will probably have it fixed some day, but I want to try digital for a change. For more or less static pictures, I have an even older Canon A1 that I love too.
Thus, the FZ will do mostly kids pictures, and the good ones are closer to sports (or war ;)) shots than anything else. It looks like both cameras are exacty what I need, although, as you probably understood, right now I seem to prefer the FZ5 (at least on paper).
So, to answer your question, yes the difference between a focus lock in 0.2 second and another in 1 second matters to me, as kids don't wait and I confess having no particular talent to compensate for it. My IS3000 focused 99% of the time almost instantaneously, and I would really miss this.