We switched from Apache to lighttpd back in the day specifically for performance issues; the other option would have been to add a new server. This wasn't "Facebook scale": just a small company with 2 devs running a few sites with quite a lot of pageviews.

Since then computers (and presumably also Apache) have become faster and I don't really know how it compares today, but at least in the past it really did make a significant enough performance difference to care about.